Recently I installed the corksport exhaust and J-pipe in my car (waiting for more time to install S-pipe). Of course it set off the CEL and the car was running very rich to the point you could sometimes smell the gas. During this timeframe my gas mileage remained around 31 mpg. I tried to install the resistor/capicator fix but this only worked for about 2 days. I finally got around to installing the spark plug non-fouler solution. Since this time my gas mileage has gone down tremendously -- to about 20mpg. My complete set of upgrades are: Injen intake, Forge BOV, Unichip, Corksport J-pipe and exhaust. Does anyone have any idea on what could cause this? It doesn't make sense to me that I'd get better gas mileage with the CEL on vs off. My next step is going to be changing my spark plugs - they were planned anyways.