Adding a resonator such as Dynomax Race Bullet after the cat would help alot. That what I'm using along with Dynomax UltraFlow out back. All 3" thruout. They're amazingly quiet (no drone). HTHSupraFiend said:well I'm good in the exhaust department now so my opinion doesn't really count but I just went through a whole bunch of work to convert my entire exhaust system to 2.5 inch piping. Putting 2.25 muffler on just seems like a step forward then one back. Unfortuanly my 2.5 inch Ultraflow is loud as hell, I need to add a resonator, I've got a nasty buzz.