Should be able to find a decent port 2g exhaust manifold for cheap on various DSM forums.
Plastic screw on TB is your BISS screw, it fine tunes the idle. Replace it otherwise you'll start to idle surge eventually if you already aren't.
Stock FPR should keep you in good hands for a while, when you start hitting low 12s you might consider an aftermarket setup. Stock fuel rail flows surprisingly well.
You should stop by the MSP Grand Opening on Sunday, they're hardcore DSM junkies there.