I'm doing my first autocross on Jan 6th with my 2017 Ford Focus ST. When I signed up I had to input my class. A quick read of the SCCA rules and I picked GS. I'm new to this and upon further reading I think I'm STH as I have ECU tune (Ford Procal). I also have the RS air intake box with K&N filter and the ford performance catback exhaust. So is STH the correct class then? I assume this can be changed easily enough on race day.