So i got my magnaflow put on and it has a little more perrr while at idle but when the engine gets heated up and i am moving it makes a load "rattleing" noise and i don't know if it is and exhuast leak or a bracket broke loose and it is vibrating... when i first got in on and drove it home... there was nothing.. i drove it a couple days later to a place about and hour away from where i live and i noticed about half the way there this noise but only when i was on the gas so i though it was a leak... however, when i am in park or nuetral and rev it up a little there are no unusual noises like the one i am hearing... most of the time it makes the noise while i am on the gas and just starting to go.. once i get above 2500 though my new wine from my intake and all gets a little loude itselft so i can't tell if it is still making it.. a few times though going over i guess "bumpy roads" and wastn't on the gas i could here the same noise and i think it is just vibrating somewhere.. i was away from my home so i couldn't jack it up or anything but i kinda felt the muffler and stuff kinda wiggled it back and forth but i didn't seem like i was really "loose" enough to make any noise...

and suggestions i can get would be appriciated and by the way my pulley'* come today and i'm off school tomorrow so more fun for me when i get the exhuast fixed

thanks guys

Assuming you only replaced the muffler, and not the catalytic converter, make sure the heatshield on the Cat isn't loose. That happened to me once. And it'll only be obvious at a certain RPM (resonance). Also check for ANY other obstructions that it might be rattling on. Bright spots will appear on the exhaust where it'* happening.

Make sure both rubber bands are installed on the cat hanger, and that both muffler hangers are tight and the rubber is intact.

i'm sorry i didn't make myself clear... i got a new cat. and not a new muffler sorry about that i shoulda said so.... shoudl i still check for the same stuff

Same stuff.

alright thanks i'll jack it up tomorrow and take a look... do most shops that do stuff like that have a warenty at all? i'm from ROLLA Missouri lol it was some hick little shop but there was nothin else here so i had to do it there

After I had mine installed the heat shield over the muffler fell and was being held up by the muffler itself. Don't know how it happened, but a couple of sheet metal screws later its nice and snug.

The heat shield on a cat converter is typically welded on and with a couple heat cycles one of the welds may have been loose and let go.

Happened to me a year after it was installed.

i took my car back to the place where i got the cat. put on... me and the guy there could find nothing loose that would be vibrating.. however, part of the hanger for the muffler on the right side was very close to part of the trailer hitch we pulled it down a little with a crow bar and it helped some when i drove it around after that but i still hear some noise he said it could something loose in the muffler, but i dont' know if it is just the sound since i got my cat. put in cause it doesn't sound "wronge" but i'm not sure what is supposed to sound like

Can you record and post a link to a sound clip?