The SCCA class I'm running does require a dyno cert for the season. If I were using an electronic throttle body that would be an option. Unfortunately I have a cable throttle body.I do not know how to tune but just started with HPTuners for the s550. I think if you need to prove HP on dyno like with NASA ST classes you can tweek throttle position and limit power. One of the NASA ST2 guys did that with ST2 to ST1 cross classing in the C5 vette and it worked fine. SCCA does not require dyno proof so put everyone in the same boat with listed engine mods and restrictor plates. So this same guy swapped plates for T1 and GT2 and used his HPT to download the corresponding tunes per restrictor plate.
That's what I'm doing next week getting 2 dyno tunes one for T1 no plate and T2 with plate and using my HPT to swap tunes as needed. Smarter guys double their costs doubling the number of tunes for 93 pumpgas for when the competition is light and 100 octane for the extra edge when $8/gal race fuel makes sense.