I just installed ZZP mid header and their catted 2.5" downpipe. WHen its cold it sounds all rattled and crazy. When it warms up i don't hear a drop of rattle. Are the spun metal cats expanding and stopping the rattling when it gets hot? We heat cycled it once and tightened bolts up, will do it again soon in case.

 

i have just the downpipe, and it's raspy as **** when it's cold. i deal with it.

 

i agree, but its actually sounding like its loose. Then when it warms up it sounds MINT

 

I originaly thought it also was loose or leaking. i went over it with a fine tooth comb. no clearence issues no heat shield rattle and no leaks. i even went as far as replacing the muffler thinking it was the cause but it turns out it is just how it sounds. i have grown on it and it dosent phase me anymore. also its getting warmer out so i dont get the sound as much.

 

I was thinking maybe it was the catback on the car. It has a resonator on it, IDK if those can break or not. But since I am getting this feed back I almost dont care now lol

 

a new resonator will quiet it down a bit.

 

I think I got the same noise around the downpipe area during cold starts... sounds almost like heat shield is loose or something?

 

Exactly!!!