Poor Acceleration/hesitation (mid-range only) @ full throttle only (FIXED)

[MarcoPolo]

car hasn't gone to the shop yet but hopefully soon. in the meantime, i wanted to take a stab at either inspecting some things myself or being able to run some test.
Car is an '06 6MT. Mainly used as a Track/HPDE vehicle. street driven.
took it out for the first event of the season and i'm getting a shuddering/hesitation that only seems to be appear on full throttle and ONLY below 4.5/5k.

Scenario 1: i'm at low RPM and go WOT...car will poorly accelerate (feels like misfiring) until about 4.5/5k and then it goes away and pulls no problem.
Scenario 2: i'm at low RPM and go 50-75% throttle....car will accelerate perfectly fine and when i reach 4.5/5k, i got WOT and the car drives like normal.

for this weekends track event, once i figured out the symptoms and realized i can work around it, i stayed tracking and either a) stayed above 4.5kRPM (pretty hard in some turns @ NJMP Thunderbolt) or b) if i had to dip below 4.5k RPM, i was at 50-75% throttle.

it doesn't matter what gear i'm in, this occurs. street testing i've done it on 2nd but on the expressway, i can easily replicate this on 3rd, 4th, 5th, and 6th.

exhuast setup prior to off-season:
AFE intake, Euro Headers, Euro Section 1, SS Res Sect 2, SS Race

Off-season work prior to this event
- swapped Section 2 back to stock.
- replaced weathering AFE intake boot and reinstalled
- oil change (15w50)
- replaced CV Joint gasket - mechanic noticed grease, so removed and noticed gasket was gone. replaced and re-packed with grease.

Coil Packs were done by previous owner @ 140k (~23k miles ago)
Spark plugs were done by me @ 150k miles (~13k miles ago).
Throttle actuator and TPS by Oil filter were done last year.
Swapped neighbors accelerator pedal last night and problem still persisted. even so, INPA shows that my accelerator pedal values did not go crazy.
my LTFT's are @ -3 and don't seem to be fluctuating. my STFT's zero out when i go WOT.
Bimmerworld fuel starvation kit done in 2020
Vanos Rebuild done in 2020.
Fuel filter and fuel pump are still original

Some VIdeos of the issue:
https://www.youtube.com/watch?v=VA8vATrMnpM - in this video, i go WOT and it you can hear the misfiring/poor acceleration and then at 4.5/5k RPM it goes away and seems to drive like normal

https://www.youtube.com/watch?v=MJnGsrfmRVU - in this video, i do 2 2nd gear runs. i first go 50/75% throttle and it accelerates fairly normally. at the 2nd run, i go flat out and you can hear the hesitation. a bit harder to hear in 2nd gear but you should pick it up.

i understand these cars can sometimes be a game of "throw parts at it". if that is the case, then please share what i should just throw at it just to do it. otherwise, if anyone thinks there is any testing i can do, great.

i'll do my best to update this top thread as i chase this down. sucks as this is the beginning of the track season.

any assistance is appreciated.

update1:
INPA codes that showed up were 130, 230, 174, 175.

[oceansize]

VANOS solenoid or broken tab on exhaust hub, check for codes, clear codes, if comes back immediately probably hub.

[MarcoPolo]

VANOS solenoid or broken tab on exhaust sprocket, check for codes, clear codes, if comes back immediately probably sprocket.

INPA codes as of yesterday were 130, 230, 174, and 175. i cleared them yesterday. ran a few times and nothing came back. will run again today.

i did read up vanos yesterday. let me ask you. vanos was rebuilt in Feb. 2020. assuming a proper rebuild, could what you mention break / go bad again?

pulling up the notes on my vanos rebuild, this is what they wrote:
"Remove valve cover and fan assembly, Set timing and remove vanos from engine. Disassemble and replace all shims and seals. reassemble, valve adjustment". parts purchased: rattle repair kit, seal repair kit, VVT Seal plate, VVT housing seal plate, intake/exhaust sprocket bolt set, vanos filter.

[MarcoPolo]

VANOS solenoid or broken tab on exhaust hub, check for codes, clear codes, if comes back immediately probably hub.

more notes on vanos rebuild from my emails:

Them: We removed the vanos and inspected your hub and oil pump disc. If these are the original parts, we are impressed with how good of condition they are in. The oil pump disc has very little impact which indicates that there isn't any excessive play between the hub and disc. With this being said. we can leave the pieces alone or we can upgrade the disc if you prefer. Upgrading the disc will allow for even tighter of a fitment around those exhaust ears. We think your parts are OK to reuse but let me know your thoughts.

Me: .I'm comfortable reusing the disc. One of your first emails mentions "Upgraded oil pump disc bolt set (for intake and exhaust) " Is that still getting done? Imagine so but just confirming.

Them: No problem and yes, you will be getting upgrade intake and exhaust bolts. They’re notorious for backing out (the bolts that bolt the timing gears onto the camshafts) so they will replaced.

[oceansize]

Those aren't VANOS related codes. Could be MAF, intake manifold issues such as the boots have come loose, vacuum leaks, O2, TPS, trims, fuel pressure regulator....

FYI: They didn't replace your exhaust hub meaning you still have the original more than likely and the tabs are known to break ( I didn't see your previous post so you know this).

[MarcoPolo]

Those aren't VANOS related codes. Could be MAF, intake manifold issues such as the boots have come loose, vacuum leaks, O2, TPS, trims, fuel pressure regulator....

FYI: They didn't replace your exhaust hub meaning you still have the original more than likely and the tabs are known to break.

thanks. will pass along this info to my mechanic. hopefully squeeze it for this week before my next event. he's leaning towards throttle-related although i think i've tested it enough to confirm that it's not that. but, i'm not the expert here. i'll let him go down his list of diagnostics.

[eacmen]

more notes on vanos rebuild from my emails:

Them: We removed the vanos and inspected your hub and oil pump disc. If these are the original parts, we are impressed with how good of condition they are in. The oil pump disc has very little impact which indicates that there isn't any excessive play between the hub and disc. With this being said. we can leave the pieces alone or we can upgrade the disc if you prefer. Upgrading the disc will allow for even tighter of a fitment around those exhaust ears. We think your parts are OK to reuse but let me know your thoughts.

Me: .I'm comfortable reusing the disc. One of your first emails mentions "Upgraded oil pump disc bolt set (for intake and exhaust) " Is that still getting done? Imagine so but just confirming.

Them: No problem and yes, you will be getting upgrade intake and exhaust bolts. They’re notorious for backing out (the bolts that bolt the timing gears onto the camshafts) so they will replaced.

would highly recommend changing the exhaust hub disc for the beisan one and/or new exhaust hub. especially if they are changing the cam bolts. it would be no extra labor

you can’t really tell if the exhaust hub tabs are compromised just by inspecting it.

since they are also doing cam bolts should also change upper timing tensioner guide

[MarcoPolo]

update:
cyl 5 and 6 misfire. mechanic is going to inspect/replace plugs and move coil packs around. we're getting somewhere.

[MarcoPolo]

update:
cyl 5 and 6 misfire. mechanic is going to inspect/replace plugs and move coil packs around. we're getting somewhere.

correction. it was misfires on all of bank 2 (cylinders 4, 5, and 6). plugs replaced and coil packs swapped. still same misire on 4, 5, 6.

still being troubleshot.

[sapote]

Me: .I'm comfortable reusing the disc. One of your first emails mentions "Upgraded oil pump disc bolt set (for intake and exhaust) " Is that still getting done? Imagine so but just confirming.

Them: No problem and yes, you will be getting upgrade intake and exhaust bolts. They’re notorious for backing out (the bolts that bolt the timing gears onto the camshafts) so they will replaced..

Even this is not related to the current problem, for track application, I think it is safer to update with the smaller holes for the pump disk before the hub driving taps broke.

[Obioban]

Cylinder 5/6 I'd worry about a head gasket.
Cylinders 4/5/6 I'd assume the issue is a precat 02.

In either case, I would absolutely replace the vanos pump disk with something with the smaller holes (e.g. Beisan)-- inspection is meaningless other than telling you that it hasn't failed yet (but still could later that afternoon).

[MarcoPolo]

Appreciate everyones concern regarding the vanos i will reach out to the shop that did the rebuild and see if they know more (was it previously upgraded perhaps)

FIXED
Mechanic could not figure out what the issue was. he didn't want to throw parts at it as he was following the data. at the end, he compared the temps at pre and post-cat and noticed a 50 degree drop on bank2. he suspected a clogged cat. removed it and inspected it and while he didn't hear anything, the color of the mesh inside the cat was different. i happened to have a Rogue Rasp eliminator v2 that i had installed previously but removed because it was a bit too loud. we put that back on and the car is 100%. just in time for this weekend lightning event @ NJMP.

[jdamore44]

Appreciate everyones concern regarding the vanos i will reach out to the shop that did the rebuild and see if they know more (was it previously upgraded perhaps)

FIXED
Mechanic could not figure out what the issue was. he didn't want to throw parts at it as he was following the data. at the end, he compared the temps at pre and post-cat and noticed a 50 degree drop on bank2. he suspected a clogged cat. removed it and inspected it and while he didn't hear anything, the color of the mesh inside the cat was different. i happened to have a Rogue Rasp eliminator v2 that i had installed previously but removed because it was a bit too loud. we put that back on and the car is 100%. just in time for this weekend lightning event @ NJMP.

Glad it cleared up, so the cats had about 160K on them?

[MarcoPolo]

It was a euro section 1 I picked up 2 years ago. Mileage unknown. I put about 20k on them.

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