ECU Pulling Timing / OAR Changes Under WOT | Looking for Input

[HAHAFiST]

Well aware this could turn into a big can of worms on the internet, but genuinely looking for useful input here, or maybe some PIDs I can start checking on the COBB AP to help diagnose before I start getting into more mechanical issues. Anyone else in CA experiencing this on their 91 octane tunes?
ECU Pulling Timing / OAR Changes Under WOT | Looking for Input
Issue:

• ECU pulling timing and adjusting OAR during WOT pulls on both 91 oct and E30 tunes
• OAR sits between -0.78 and -0.84 on 91 oct tune during WOT
• Issue only occurs under high load — smooth at idle and normal driving

Fuel:

• CA 91 octane should be ~E10, recent sample tested at E5–E6
• Adding a gallon of E85 to either the 91 or E30 tune resolves the knock and OAR changes
• Tested two different 76 stations — issue persists at both, worse at the second

Recent Changes (~1 year ago):

• Timing belt replaced - everything was dead on with double checking the timing locks and rotating the engine severals times back to TDC.
• AWR 70A durometer passenger engine mount installed... I might swap back to the stock mount just to rule this out.. but does NVM result in OAR changes?

Checks Performed/Observations

• Spark plugs — no fouling, gap correct
• Charge temps — 5–6°F above ambient during WOT pulls
• IAT — stable during pulls, not spiking
• Knock appears mostly even across all cylinders during WOT
• Compression check: All cyls hitting 180+ psi

 

[Grsemky]

Well aware this could turn into a big can of worms on the internet, but genuinely looking for useful input here, or maybe some PIDs I can start checking on the COBB AP to help diagnose before I start getting into more mechanical issues. Anyone else in CA experiencing this on their 91 octane tunes?

Not California but Cali gas in Arizona, I have a Dizzy stage 2 91 and it will pull timing when boost comes on and my OAR will drop, it does recover quickly when I'm cruising. I find adding half a can of Octanium from VP fuels, to a full tank solves the issue. I think that amount added to 91 will net 94oct, which just really showed the gas quality isn't great and I've tried multiple different brands and locations 🤷🏼‍♂️

 

[HAHAFiST]

Not California but Cali gas in Arizona, I have a Dizzy stage 2 91 and it will pull timing when boost comes on and my OAR will drop, it does recover quickly when I'm cruising. I find adding half a can of Octanium from VP fuels, to a full tank solves the issue. I think that amount added to 91 will net 94oct, which just really showed the gas quality isn't great and I've tried multiple different brands and locations 🤷🏼‍♂️

Not California but Cali gas in Arizona, I have a Dizzy stage 2 91 and it will pull timing when boost comes on and my OAR will drop, it does recover quickly when I'm cruising. I find adding half a can of Octanium from VP fuels, to a full tank solves the issue. I think that amount added to 91 will net 94oct, which just really showed the gas quality isn't great and I've tried multiple different brands and locations 🤷🏼‍♂️

Yeah, similar. If I add a gallon of E85 while on a 91 oct tune... everything corrects. I didn't need to do that before is the issue. Someone on reddit said I should've performed the misfire correction programming with Forscan after my timing belt job so I'm gonna tackle that and see what happens.

 

[Grsemky]

Let's us know your findings, I'm on a stock timing belt and currently at 100k with similar issues so I'm skeptical it's that... Especially since the issue is only under high load vs all time which would be a timing issue

 

[HAHAFiST]

Let's us know your findings, I'm on a stock timing belt and currently at 100k with similar issues so I'm skeptical it's that... Especially since the issue is only under high load vs all time which would be a timing issue

Totally, it could be something else like higher temps, carbon build up or other things are at play

Let's us know your findings, I'm on a stock timing belt and currently at 100k with similar issues so I'm skeptical it's that... Especially since the issue is only under high load vs all time which would be a timing issue

So you've changed absolutely nothing about your car, no timing belt work... no new tunes, same fuel etc.. and you have this problem? If a large group of people in CA said "Hey... I need to add octane to make my car not knock...I've been on the same tune forever..." then I'd suspect its a pump gas fuel problem.

 

[Grsemky]

Totally, it could be something else like higher temps, carbon build up or other things are at play


So you've changed absolutely nothing about your car, no timing belt work... no new tunes, same fuel etc.. and you have this problem? If a large group of people in CA said "Hey... I need to add octane to make my car not knock...I've been on the same tune forever..." then I'd suspect its a pump gas fuel problem.

Correct same tune everything, I changed my mounts but no change to timing corrections, only if I use a higher octane rating...