Okay, havent been on here in a While but here goes. I have a 2.8L 30V with STOCK CATS and 2.5inch pipe from the cats back, no RES, to a 14816 Magnaflow. I have this stupid BUZZ too. It happens when anything past 1/3 throttle from about 2500rpm-3500rmp. Im really thinking its the cats....cause besides my cats....everything is bran spankin new on my exhaust. Full Custom, mandrel bent. I think im going to cut off my Muffler and go for a spin to see if the BUZ goes away. if its still there....its gotta be the god dam cats....

Any updates on this?...

 

Bump?

 

Gawd... peeps, its called a 'resonance'. You are vibrating.. tighten things up, or try loosening them.. anything to change the resonance frequency.