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

 

[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 🤷🏼‍♂️