I recently installed a cat-back exhaust, but now it makes a loud noise and vibration under these circumstances
during snow/rain
decelerating
low RPMS
after car warms up

any ideas as to what the problem is?

 

You check for leaks or improper seals?

 

yeah, it works just fine in the warm weather, but for some reason when it rains it acts up.

 

Tighten any loost bolts and check your intake?

 

My Apexi WS2 does the same thing and I have yet to figure out why!

But it also would do it when I did it in reverse, or really bad when i would go about 60mph and then let off the gas. I could see where my exhaust was tapping a nit because of the cratches, it was the bend that is between the passenger front and back doors. You'll see a nut there. I just put a couple coats of RTV on there, and its fine now except reverse here and there and in the rain.

 

Any other ideas? When it does it in the rain simply blows my mind away. How can water affect it liek that?

 

go back to the shop where you installed it, they should have more experience with this