I don't have power specs for the S parts (and at least for now, you can replace the engine for free to restore it to stock), but the Himedic gets the high lift camshaft s, titanium conrods and carbon propshaft.
The only ultimate parts for the GR Corolla are titanium conrods and carbon propshaft. I don't have power numbers though because unlike the Himedic, it does cost credits to replace the engine.
The Corolla seems to have pretty small RPM gains compared to other cars. For example, the titanium conrods only add about 150 RPM, not 400-500 like they would on other cars.
