I did a search and found this site. Very cool. You just plug in a retailer to do a search for the code. Nashbar and Performance came up. Couldn't find Supergo.
The Performance code 6000387 is for 20% off untill 12/31/04. Not sure if it works....yet.

http://www.coupon-codes.net/

Performance had a sudden awakening to the rampant use of their coupon codes and canx most of them, including the one you posted. However, there are some that work with the caveat that if you cannot use them with your team membership. The website will let you, the invoice will show up in your email, but your credit card will be billed without the coupon discount. If you use the coupon, don't log in as a team member.

I think that codes been dead a long time, see here: http://forums.roadbikereview.com/showthread.php?t=7705

Here's another good site: http://www.edealinfo.com/Coupons/performancebike.shtml