hey guys,

i was cruising on the highway yesterday in 4th gear at 50-55mph when the check engine light popped on (steady). i got the code pulled..P0420, exhaust inefficiency or something like that. i have an uppipe and TXS stealthback with a highflow cat. my question is...i've had my exhaust mods for over 2000 miles and i got a unichip about 1000 miles ago (9000 on car now), why is this CEL coming on now? yesterday was the first time i ever got Sunoco Ultra 94 octane gas, could that be what caused it? (i've always used either 92 or 91 octane) any harm to my car by leaving this on? should i reset the ecu?


thanks,
Anthony