I picked up a cheapie $100 cat back off of ebay - seller was speedyracerparts. Installation was a little fiddly - not too bad for me, as I work as a mechanic at my second job and had the car up on the two post lift. That said, the exhaust burble is nice and deep without being too loud. As for the performance gains - I have no idea about the numbers, but the car is a lot more responsive now. I also did the stealth CAI earlier in the week and that made a difference. For less than $150 all in and about an hour of my time, I'm back in love with my car. I can now hold off a bit longer on that 2013+ Focus ST that I'm lusting after. (don't want to get into another car loan quite yet - I'm liking not having a car payment...)
07 ZX3 SE MTX - enjoying every minute with it
MacBook Pro 15"