Hi, I recently purchased and installed a new Monza Pacesetter Cat-Back for my VW Golf GTi VR6. Only after cat back was installed did my car start making at very very LOUD whistle/honk sound when a certain backpressure is reached (around 3000 rpm under load and more than half throttle). My car sounds like a $#@#-ing train going down the street and can be heard from blocks away.

Regardless, I can't enjoy it like this and I need to find out what to do.

My plan so far is to:
Try a different muffler and see if it still makes the sound.
try no muffler (if I cant get another to try) and see if it makes the sound.
If it doesnt make the sound then I guess its the muffler (tips I think)


Anyone ever heard of this before? could I have damaged something that would contribute to this sound changing the cat back?? could exhaust leaks make this sound? a mechanic suggested getting the whole system welded on instead of clamped.

Help?!?!?

It sounds like maybe a baffle didn't get properly welded in either the cat or the muffler. It vibrates under certain conditions and makes some odd noises.

well, thats what you get for buying the cheapest aftermarket exhaust in the world.

Either that or Bubb Rubb snuck into your garage while you weren't looking and installed some whistle tips woowoooooo!

yeah it is cheapest for sure and that is what I get. However, it is still a nice sounding exhaust when it isnt whistling. Think I might just buy a remus muffler and ditch the monza one. You don't have to be a cock about it though, thanks for the great help douche. peace