My setup is all Megan Racing.
4-1 2.25" Header
2.25" Downpipe/Testpipe
2.5" Drift Spec Exhaust
Fit:4 Exhaust touches the body a bit under passenger seat, but its random as hell, headers and downpipe are perfect fit.
Power:4 You can feel the difference from stock header/downpipe.
Loudness:3.5 It can be loud if your at half to wide open throttle. You can hear my intake more than the header back exhaust.
Some pics:

^^ BTW I know this is exhaust thread but I also love my Megan Racing EP3/DC5 Rear Lower Control Arms.

^^ Not the best header shot but you see em.. kinda. And my ebay CAI, Skunk2 Engine dress up.