I'm wondering since my car came stock with a lsd dif is this going to keep me from being able to run in the stock or sts class? My car is a 87 rx7 gxl with header, turbo exhuast, and intake plate soon to be street ported though, but will this knock me into a different class?

Take a look at this thread:

Auto-X FAQ. (http://www.automotiveforums.com/vbulletin/showthread.php?t=116168)

That will tell you what is allowed for each class. Also, you can visit your local chapter’s website and find out limitations for each class. If your car came with an LSD from the factory then that won't keep you from running in the stock class.

does your car have 4 seats? if so it currently qualifies for STX.

if not then it is in ST2.

porting will move you up to CSP

your header is what makes you illegal for stock.

Well it orignally came with back seats however I pulled them and installed the storage bins out of a turbo2 donar car, and thanks for the info.

if you don't put the seats back in then you're in Street Mod.