I autocross a lot, and I've got it dialed in pretty good. I started out completely stock 04 NA, and added:
SRT brakes
SRT springs (cut about 1/2 -3/4 coil all around)
AMG shocks
SRT front sway bar
Front camber bolts (only adds about 1/2 degree neg camber)
Rear camber arms (actually to get less negative camber)
74mm TB
NeedsWings CAI, with K&N filter
Eurocharged tune
Resonator delete, straight-pipe replaced
Hoosier A6 Front 245 35 18, Rear 265 35 19
1/4" hubcentric spacer on front wheels
oil catch can
aggessive alignment (twitchy on the street, but quick turn-in at the track)

This moved me up to DSP in SCCA and D in NASA, but I won both classes last year in my region. With this setup I only didn't finish first twice. Once when I corded my tires, and the other time when 5 Pro racers showed up in my class -- but I did beat two of them. I was barely in DSP, and a few of them were at the cutting edge top with very wild setups.

If you want fast times, do the Hoosier's first. If you want to have fun, do the resonator delete first.
Best of luck.
Mike