Some pics of my car from a recent SCCA Solo autocross event at Firebird Raceway earlier this month. There is another event on March 4th so if you live in the Phoenix area, come on out.
What class do you run in?
ESP. I never come close to the fast guys in my class. Haha.
Did you modify with intent to auto-x or did you just modify how you wanted and decided to go auto-x?
That's half the problem. certainly modifications over others (especially for high powered cars like the mustang) can easily land you in a class that you're just not competitive in.
Same thing happens in TT for NASA. you've got to be VERY careful with what and how you modify the car. Otherwise you end up in TTU with 700 hp, coil-over equipped Corvettes.
In your case it looks like at the very least you've got plus sized wheels and tires and some lowering springs.
Just going back down to your stock wheels and rubber may get you back in to a category that you're competitive in. Obviously the springs are a bit different. They take a little more work to get out.