Was trying to find info about the PTU/RDU for ya @Skv0ra but I'm not familiar enough with the specifics of the RS to find quick info on it, but it sounds like the "rear drive unit" on the RS isn't stout enough to handle much higher power in racing applications.
@Skv0ra everything outrun my mustang but it was still very fun to drive and reliable. everyone now has newer mustangs and newer camaros... way outrun what I had