i have a 00 civic si. it has DCsports header, aftermarket at, and straight pipe back to a muffler. for some odd reason i keep getting this rattle in the exhaust. i think that it is between the cat and the header. i have done everything i can think of to fix it. i out a exhaust donut on, then put a different one, then took them all of. nothing seems to work. and yes it is tightened down really well. was wondering if anyone else has had this problem. any help would be greatly appreciated. thanx

 

I have this problem with my Apexi N1 system. Wondering how to fix it as well.

 

i had this problem... mine was b/c the exhaust tip was hitting the rear bumper. it was not really secure on the rubber hangers... i put o clamp things aroudn the rubber hangers and tightened it up. it doesnt rattle anymore

 

I had this problem as well before but it calmed down after my car heated up. I just took it to a garage where they did a once over and tightened everything. It no longer rattles even when its cold.

 

could be a heat shield above the cat or the mid-pipe. it could also be the midpipe banging on the gas tank too. what i would do is i would get under the car and just grab ahold of the exhaust and just move it from side to side and back and forth, that should help you figure out where the rattle is or if its the exhaust hitting anything.