2010 Silverado Exhaust Noise Question?

[zachcopp]

I have a 2010 Silverado Extended cab with the 5.3 liter V8. I recently had a muffler welded in and a new stereo installed. Oddly enough I began to notice the noise after I had the stereo installed, not when the muffler was welded in. It is an airy, chirpy noise. Noises are always difficult to explain. It almost sound like air is leaking from somewhere, and gets louder the higher the engine revs. It is also noticeable when the engine switches from V8 to V4 mode and vise versa. I took it to the dealership since it is still under warranty and they said it was simply a product of getting a new muffler (I think my dealer is suspect as I have taken it in for multiple issues that still have not been corrected). The noise does sound like it is coming from the front of the vehicle, kind of in the lower driver door kick panel area. The exhaust shop did not touch anything from the muffler up, so I doubt it is a muffler issue. I did take it by their and they could not audibly here any issue with the muffler. The noise just gets really irritating. The best way to describe it is an airy chirpy noise that gets louder as the engine revs, and starts to chirp when the V4 mode is engaged. Can someone please help diagnose what the issue may be. I have driven and owned multiple trucks with exhaust systems and never experienced this. The muffler is a cherry bomb extreme, and the system is only catback. Thanks for any help! I really want to get this figured out, it is annoying the heck out of me... As I said, I began to notice the noise after I had the new stereo installed. Just for the record it is not a static sound or anything. Thanks again!