21 PSI? I don't know what mods you've done to your car, but I hope you have a new fuel pump and injectors already. If not, be prepared for detonation. At least, that's what I've read from most places. On the stock fuel system, ~15 psi is max. However, I don't know your mods, so if I'm wrong, I retract this entire post and apologize. Btw, I'm a big DSM nut, so if you want to look into places with parts/advice on your dsm, here's a few rlly good sites:
www.dsm.org ****
www.dsmtuners.com ****
www.machv.com ****
www.vfaq.com ****
www.dsmtalk.com ****
www.dsmreviews.com
www.dsmparts.com
www.dsm-performance.com
www.extrememotorsports.com
**** = absolutely invaluable resources
oh, and for when you get your S-AFC
http://members.rogers.com/mrjackson9...AFC_Tuning.htm
a pretty good introductory guide
PapaShlapa