You can find the proposed rule changes for STU and STH here on page 40 of the 2020 Fastrack archives (it was from a month or 2 ago):
https://www.scca.com/downloads/49413-2020-03-20-fastrack-solo-all-thru-april/download
Here is the rules proposals part:
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Street Touring Category
#28321 Make STU Great Again!
The STAC is seeking member feedback on changes to increase participation in STU. While the focus is on STU, there are changes that would affect STH as well. These changes encompass both additional allowances and new vehicle classifications. The changes below are provided in outline form, and specific rule wording will be presented in future FasTracks pending member feedback on the overall concept. Various letters and slowly declining participation in STU has resulted in the STAC re-evaluating the Street Touring ruleset to ensure it is meeting the desires of the membership. The STAC is concerned that the Street Touring rules have not kept up with "common enthusiast modifications" and as such is seeking member feedback on the following additional car classifications and rule changes. The cars listed under Proposed would be added to Appendix A when the rule changes go into effect. The cars listed under Potential would be evaluated for inclusion in future years.
Goals of this Proposal
1. Increase Participation in STU
2. Modernize the Street Touring ruleset for turbo cars
3. Preserve competitiveness of current STU cars
4. Decrease average age of competitive STU cars
Proposed allowance changes:
1. Change max wheel width for all vehicles in STU to 11". Max tire size for all vehicles 315
2. Expand the existing intercooler allowance to include STU
3. Turbocharged vehicles may make mechanical changes to the boost controls such as replacement of electronic boost control solenoids, blow-off valves, removal of restrictor pills, etc. No changes to the turbo or wastegate. This allowance would only apply to STU and STH and follows current SP rules.
4. A new clutch allowance following the LP SP rules. Clutch friction surface and flywheel must remain OE diameter and OE number of friction surfaces. Allows for converting from dual mass flywheels to single mass flywheels. Clutch slave and master may be replaced. This allowance would only apply to forced induction cars in STU and STH.
5. Tuning for automatic/dual-clutch transmissions and electronic differentials
6. AWD vehicles may substitute one differential regardless of how many it came with from the factory
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