i got a 2003 wrx brandnew
have intalled the greddy evo catback on it...
thing is ever since then. if i run on the freeway abit hard and then lift my feet of the gas the car in gear i can hear knocking sound from right under me. it sounds like its coming from where the downpipe connects to the exhaust? o_O
I check under the car i don't see any signs of scratch or dent so the sound is not physical. there is no parts rubbing.
i checked the exhaust tip and the thing have not broke in yet so its still clear no signs of black residue