Jeff,
Couple things...I noted my max boost dropped when I installed higher performance exhaust (mine is an SSI system). Rather than change wastegate springs, I just put in a manual boost controller. The "dial-o-death" knob is in the engine compartment, so I don't have temptation to crank it up as may happen with cockpit adjustability.
Regarding clutch, my car had a basically brand new OE pressure plate and standard Sachs spring center clutch disc. I have no slippage issues, and that's with something around 375 wheel HP. YMMV.
For brain pickin' just PM me sometime and I'll give you my cell number. If you're ever near to Jersey City, look me up. I'll show you my little workshop and current project:
