I have a 08 g37s coupe. I bought a magnaflow catback exhaust and berks HFC. It sounded nice but not loud enough for my taste. But i noticed when i step on the gas hard or im downshifting it has this annoying rattling sound almost embarrassing to step on it. So i then decided to replace just the magnaflow muffler to greddys everything else still magnaflow. Now sounds good and loud but still same problem with that rattling. I took it to a muffler shop and they said its 1 of 3 things 1- it could be the flex pipes, 2- the xpipe is causing the issue and maybe might be better to put a hpipe or 3- the HFC i put on are to much for the xpipe and magnaflow probably did not take that into consideration. But he replaced the flex pipet to a diffrent style. and now its not as loud and annoying but still noticeable.any ideas on what i can do to fix this or if anyone had same issue.

 

Does it sound something like this

 

Is it actually a rattle or is it raspyness?

if its a rattle make sure all of the exhaust flanges are tight. check all of your heat shields, a loose one can rattle/tap on the exhaust. make sure your O2 sensor is not hitting something, like a heatshield or the underbody.

If its raspyness you can try welding in a resonator to help quite the raspyness down. i am sure someone else can chime in on how to kill rasp. but when i ran high flow cats there was an RPM window where it is was really bad.

 

Yes exactly like that. And also when i downshiftypu hear it. You know what can be causong that?

 

thats rasp in the video. you can try resonators.

 

Both The resonators are in there i didnt take them off.

 

Yeah the muffler shop double checked everything and is ok. When they lifted the car they reved it and said it was coming from the xpipe.

 

It's the HFC they are suppose to sound like that

 

Dumn question but How come couple other g37 with the HFC but diffrent exhaust you dont here that its sounds normal