i really need advices for this problem, well first of all i think that my car is not running as it should even with the mods i have i think the car ran better when the car had no mods. why can this be happening, another problem that i cannot solve is that the car when cruising down it revs on it's own even if i'm not touching the pedal and it's driving me nutz

. even but not least i think i have an exhaust leak and i dont know where is coming from and the car really smells bad on the inside plus i think the headers also have a leak. can this be a reason that the car is running so BAD

. I almost forget this, sometimes when i'm accelerating lets say at 45mph the car revs like idiot and it stumbles and does the same thing like 3 times in a row...