I skimmed through the thread again and I'm going to answer the only two questions posed by the OP throughout this thread (I ctrl+F for question marks):
1. Is anyone else in street mod?
I'm not.
2. What tires should I be looking at?
Depends on the rule set and where you want to class.
I'll be generous, and go to post 19 where you finally let us know you wanted a street tire of 200TW or higher, and here was a thread from a few months ago with tons of info on the latest batch of tires for this year.
http://www.ft86club.com/forums/showthread.php?t=82041
There are lots of other threads to look through if you have the patience
to find them with lots of information, sounds like you want the fattest rubber you can run based on the rule book you are following. Good luck.
*Friendly advice, you can't seem to accept the fact that you've created this problem yourself which seems to be "I want to run competitive local autocross with my car boosted, help me" There is so many variables that this is impossible to answer. Based on what you've posted, you either take the turbo off and go down a class or spend the money to compete (assuming your driving skills are up to snuff which is questionable given the amount of AutoX experience you've claimed, while past experience in other scenarios will help, like @
Locust says some guys spend a decade doing this before they run up front).
I would advise a shift in perspective and just go have fun and learn, speak with the people running your local group and see what options there are to get you in a class that you can compete in, they generally want you to have a good time and to keep showing up.
I hope you figure it out, Autocross recently became a lot more fun to me now that I have found a setup that I like, I've done oval racing and track days and given that I like how this car handles with camber plates I'll be bypassing C-Street even though I can't really afford an STX build right now I can spend the next few months or even years having fun dodging cones and getting better, on a much smaller scale my situation is not so different from yours. I hope you can find some joy in it too.
