I have the Borla TD and Labree resonated test pipes and I keep getting this fluttering sound. I took it to the shop and they put it on the lift and found no exhaust leaks (showed me while the car was on the lift). It sound like its coming from the H-pipe area only when the car is decelerating around 2400 - 1100 rpms.

Does anyone else have this combonation with the same sound or without?
any suggetions?

Thanks.

 

I forgot to mention I also changed the gaskets from the new ones back to OEM, but it didn't help.

 

Totally normal. I had the same thing with my Borla/Kinetix resonated pipes but I actually liked the sound.