Cat-bypass and PSE mod caused CEL

[steve00s]

I was told it could never happen but after installing Fabspeed's cat-bypass pipes along with a new Porsche Sport Exhaust (I didn't hook up the vacuum/electric switch) the CEL came on after only 10 miles. How is this possible? I did not touch any of the sensors. I already have an EVO high flow intake so thought maybe the increased air flow may have kicked the air/fuel ratio out of some parameter but kind of doubt that. I do plan on having the GIAC chip upgrade in the next couple of weeks but want to work out this bug first.

The car was sitting for several months before the install so could that have had anything to do with it? What should I try to resolve this?

On the positive side, the Fabspeed part is a beautiful piece of workmanship. It is a shame one cannot see it under the car. The chrome is first rate and the fit was perfect. I didn't expect too much HP increase without the chip upgrade but it was noticeable and the sound was a definite improvement. Absolutely no resonance with the top up.