An adjustable 968 Turbo RS wing that would fit a 944 hatch would be phenomanal. Every one on the market so far sells for $1,000+.
http://www.968turbo.de/968.html
http://forums.rennlist.com/rennforums/showthread.php?t=224742
A splitter such as the one by AIR would be great as well.
http://www.americaninternationalracing.com/gallery.asp?id=259246&page=15