For autocross any aftermarket forced induction is going to put you in a class that will be impossible to win.
For track, suspension and driver skill will give you MUCH more than any HP gains. And lots of HP is likely to cause you to exit the track at inappropriate places.
'95 Alpine M3 LTW
'00 Dakar M Roadster
'02 Topaz M3
Red/White SRF #4 (Chassis 561)