Quote Originally Posted by hayashi_1986 View Post
On another note, we don't know what he's done with the car. OP, can you fill us in with the mods you've slapped on to the car? That might help a bit in diagnosing the issue further. So in addition to the catback, did you have an intake or header installed? Pod filter? The ECU should re learn over time and adjust to these modifications, but the stock ECU can only re tune itself to a point. It will still run rich like all stock units to prevent piston failure (fuel keeps them cool). My EG use to blow black soot all over the arse of my car but never had any issues with fuel mileage, or any other mechanical issue for that matter. It did reek of fuel after hitting Vtec a few times. Totally normal. I had IHE on the car with a stupidly large cannon before. All that being less than restrictive will generally let the car breathe better, and consequently it'll also spit out a lot more excess fuel/soot/carbon deposits due to less walls/baffling in the new catback as opposed to stock.
I know why mine dose it, wouldn't have a clue about the exhaust past the cat. But I've a oem 4-2-1 headder and the cheapest cat I could get (roadworthy purpose) I have a 3" short ram and that's it for now. I don't think my car works very well which is why mine smells. But I'm sure it's just because his stock cat isn't warming up as quick as it used to and therefore letting the smell thru. Honestly i don't see the problem at idle but if his friend smells it following him, then we have a whole new kettle of fish