The Evo 9's are alot easier to get big power. Just got to Vishnu Performance Systems to see the difference in packages. To get 390hp in an 8 you'll need all these parts:
Passive Boost Solenoid Emulator
Standard Series 3” Cat-Back Exhaust
Standard Series 3-inch Down-Pipe with modular High-Flow Catalyst
Pre-Set Adjustable Camshaft Gears
HKS Upgraded Camshafts
Upgraded Fuel Pump --- $2425

And to get 400hp in a 9 you'll need these parts:
XFlash Reprogrammed ECU
Passive Boost Solenoid Emulator
Standard Series Downpipe
Standard Series High-Flow Catalyst
Standard Series Catback ---- $1995