I have a question I just installed a magna flow muffler onto my 07 WRX and it seems to be doing fine until I reach about 3,000RPM when the exhaust note makes a sudden change in sound. I understand that the faster you go the sound will get louder but it seems that it just makes a quick change from its normal sound to a real odd back firing sound. Just wanted to know if this is normal?

I should also note that just the muffler was installed using a 3inch pipe that was clamped on to the two inch pipe. there doesnt seem to be an exhaust leak from anywhere. I did not reaplace anything else just the muffler.

it should also be noted that this only happends when I'm driving. when I try reving the car it does not make that sound.

please sorry if this sounds stupid. I never have done any modifications to any car. i'm really curious if there is somthing wrong with the way the guy installed the muffler and maybe a little paranoid.

 

You could be getting air somewhere in the exhaust that's causing the backfire. I installed a magnaflow on my 3" turbo back and have had no problems. It's hard to say since you have nothing else done to the car.