I just got an O/R X-pipe.. and ofcourse my CEL is on. I can't really afford a tuner right now and I don't wana waste my money on MIL eliminators. My question is.. does the CEL effect my perfomance at all? Maybe it's just a psychological thing, but it seems like since i've thrown the CEL code i've had horrible gas mileage, worse than normal horrible lol.

 

For the 11,000th time, the rear O2 sensors ONLY monitor the efficiency of the catalytic converters--they do NOT have any impact on engine control--none, zilch, zippo, nada...

The "horrible gas mileage" is likely because you've been nailing it harder to hear the racket caused by the O/R pipe (BTW, noise level is the only measurable change to be had from O/R pipes).

You can make "MILS" for $5 or so as described on my site here...