Here is a list of websites to checkout before you post the question,"where can I find performance OEM or aftermarket parts? I'm pretty sure I got them all but if I miss any or some news ones come aviable we will work at getting them added to this list.
HyundaiCanada OEM parts from Canada, expensive but the best parts out there, you might find some of these parts cheaper on Ebay.
AEM SRI
DC Sport Strut Bar
Vibrant Catback Exhaust
Eibach Lowering Springs

Hyundai Accessory Store USA OEM parts for Hyundai's. Decent prices.

Hyundai OEM Parts Tons of OEM parts for Hyundai.

The rest are sites that have some limited parts or are the manufactures of the parts listed above.
Evofusion USA Limited Parts.
Korean Auto Imports Some Korean parts for the Hyundai.
KSPEC Another Korean website.
SFR Seoulfulracing yet another asian website.
Ultra RacingMakers of some KFX suspension parts.
AEM Manufacture of OEM Strut bar and Short Air Intake.
Eibach Springs Manufacture of Canadian OEM Lowering Spring.
B&I Trim Makers of Canadian OEM interior trim parts.
B&M Racing Makers of the OEM Short Shifter Kit.
Vibrant Performance Makers of Canadian OEM Catback exhaust.
OnderGround Design Makers of the first aftermarket bodykit.

Other useful sites:

HMAService Hyundai Motor America Service Information

http://www.miata.net/garage/tirecalc.html Tire Size Calculator

http://www.bigcustomwheels.com/rt_specs.jsp Tire Wheel Calculator for offset too

http://www.bmotorsports.com/shop/index.php/cPath/109_130_133 Different type of connectors (for headlights, turn signals, brake, ballasts, etc.)

http://www.autolumination.com/equalizers.htm Relays and resistors

http://car-part.com/ You can find junk yards here.

http://www.spoilerexpress.com/cart/store/index.asp They sell almost every OEM spoiler.

This post has been edited by rondy_: Oct 12 2009, 10:52 PM