[amg_dragon]

Doh! >.< Senior moment there. Take what I said about the 2nd O2 and switch it to the 1st sensor for A/F readings. My last spray was almost 2 years ago since my RA is my daily driver, and with gas prices on the rise again I've even removed my UD pulley and intake. Not that either one uses more gas, just that it makes conservative driving harder when it revs so much faster and sounds that much nicer on the boil.
But back to the leaded race gas, you'd agree that it can/will cause a false reading on the A/F the ecu will see, correct? The spark plug check would be the easiest if it's way rich of course, as would checking the O2 output. I'm just trying to help figure out WHY it's running rich on N2O from the info he's given. Do you think there's a possibility he's dropping signal strength to the TPS by tapping into it with his WOT sensor? I'm unfamiliar with what type of WOT sensor he's using as in mechanical micro switch or an electric tap. A further diagnostic could be to shut off the bottle and block the fuel coming out of the solenoid side and see if the problem persists.