So ever since I've converted to e85, randomly at cruise and if I hold partial throttle for a while, my wideband will completely read max lean. The exhaust will sound like a deep drone and the car will have very little power. But once I release or blip the throttle. It will return to normal.

Some days it's worse than others, never really consistent. Any ideas what it could be?

 

This back room forum is a bit sleeply. I would post this up in the main engine mgt/ tuning forum or other

 

Assuming you know the ROM and the tune are both good, a failing O2 sensor might look like you describe.

If the car has been tuned recently or the ROM has been upgraded, but your EVO ran fine before, then I'd try rolling back to the previous ROM/tune.

Or simply try a totally stock ROM and change only the injector scaling to match your injectors. Just don't go WOT.

Perhaps a bad IAC valve or even a bad MAF might cause this; if all else fails, try swapping these out with a buddy's EVO.