I'm with bmussatti on the "support our sponsors". I'd go to the sponsors page and check out what they have first. If they don't have what you're looking for you can try some of these (some are sponsors):
Sunset Porsche : Porsche brand replacements, Tequipment.
Vertex Automotive OEM replacements, upgrades.
Pap Parts : OEM replacements.
Be careful with the tune-up kits. Make sure you get the proper plugs with a heat rating of 7. They don't always have the right plugs in the kit and that can be dangerous in the long run.
Performance Products : OEM replacements, upgrades.