I'm joining the SCCA and I was wondering about slightly modifing the suspension, brakes, tires, and exhaust. Where would you start at with the modifications?

 

Just a few things...

Road racing, or autocross?

There are specific classes of competition within each. The rules for the particular class will tell you: what you have to do (rollcage?, fire extinguisher?), what you could do (tires, wheels, catback, sways), and most importantly, what you can't do (springs, brakes, turbo, etc.)

Read the rule books online.

You really should go to the track (on on here) and find a car with the level of performance you want to attain for whatever you want to do.

Also, try (reading the threads first) posting in the competition section. If I could assume that you are looking at "B" Stock autocross, we have Champions (and wanna bees) who post here regularly.

Speed co$ts. How fast do you want to go?

 

Start with the rulebook.