nastyboxster. it is the headers i had them installed before the revo chip and was already getting the cel light...i also replaced the stock muffler with a set of magnaflow ones...but i just recently put the stoch muffler back on because i got 2 stupid speeding tickets.i for 10 miles over the limt and another for 9 miles over the limt. and both times i was going with the flow of traffic and cars right next to me...i figure i was to loud and it made me the easy choice out of a crowd...
p.s. i have not noticed any loss of power after i went back to stock muffler..