As far as I know the other TR3 race FRS are not boosted.
TR3 has done many forced induction cars for road customers, but I believe their race cars only have cooling and shocks modification, aside of the gutting and interior safety.
I have not seen them all so I'll report back once I know more about the whole thing
I got a good opportunity buying my wrecked FRS locally so I decided to jump in. But I have not done that much research, I'll see how it plays out.