If you open up your exhaust you'll lose torque easy. 3" pipe is way too much, so if you wanted a hi flow cat, which are generally 3" you'd need reducers. Many people would say get a whole new exhaust if you're doing hi flow. A hi flow cat on it'* own with stock mufflers and pipe should only help. You have a supercharger so you won't have as many problems, you're pushing more air around.
I know magnaflow makes a nice hi flow cat, you could also get a matching magnaflow muffler. Then you'll love it!
'06 Vee Dub GTI 2 door Tornado Red
- 2.0 Turbocharged, Intercooled, Direct Injected, 6 Speed DSG, Underbody Aero, 17" Classix
- Moonroof, Bi-Xenon headlamps, Interlagos Plaid Sport Seats, 6 Disc In-dash, iPod integration, GTI Monster Mats (winter)
'93 Bonneville SE Purple Pearl H4U package - picked up June 23, 2003, Traded-in June 28, 2007...