Performance wise...:
Stillen headers,
better wheels/tire setup,
Bullydog GT tuner,
suspension upgrades such as front strut tower bar from racingline or stillen, rear endlings from racingline, rear sway bar-racingline or stillen (racingline is better ~cough~)
eibach prokit or tien springs for lowering ur center of gravity, (most have eibach)
fujita, K&N, weapon r, takeda, AEM intakes,
exhaust (anything but a fartcan please...)
Turbo from Speed force racing, or your own custom setup
Exterior:
stillen, ait, fox racing, razzi body, duraflex/extreme dimensions(ED) kit/components front/rear/sideskirts combos etc
carbon fiber products for hood or trunk. either OEM replacements or 'upgrades' such as vented GT style hood or imp wing integrated cf trunk
-*custom made headlights with projector housing- you need to make yourself*-
ebay LED taillights- come in black, smoke, and chrome
www.stillen.com
www.extremedimensions.com
www.racinglineperformance.com - ~~~Nico A/C Sponsor~~~
www.aitracing.com
www.visracing.com
Theres a lil bit to get you going. Dont forget to also look in the coupe specific for sale section from time to time!!