I recently put a high flow magna flow cat and magna flow muffler on my car and put 2.25 pipe in between. at about 3 grand it makes the most terribly annoying buzzing sound. It is really annoying and loud and it prob happens at around 5000 rpm too but i cant hear it over the exhaust. Any ideas how to get rid of it? There are no leaks and i talked to a few mechanics and got a bunch of different answers.One said its cuz i have headers too, one said its cuz of the straight flow design, and one said it could be the engine vibrating at a different rate than my exhaust. None of this made sense to me cuz than every aftermarket exhaust would do that. Also the heat shield isn't hitting. Thanks

 

my old civic had piping rubbing on the gas tank, over by the passenger rear shock, and it made the noise you desribed. check it out. see if your exhaust is hitting any part of the car. the exhaust should only be touching the catalytic converter flange and the rubber hangers the exhaust is hung by.

 

No its definately not that. I checked it multiple times. Its driving me crazy. Any other suggestions?

 

Every exhaust system has one or more resonant frequency peaks, particularlyduring high-load, low engine speed conditions (slight incline in top gear). Aftermarket exhaust system peaks are more noticable because their mufflers don't baffle (and restrict) exaust flow as much as do the stock mufflers.

A metal-to-metal vibration will cause a tapping sound, but if you have eliminated this as a cause, you might want to try downshifting when you reach a resonant peak. It works for me, but I really don't have to do this too often.