What we need is an addition to the Tuning Shop for the more exotic parts and engine swaps.
But to ensure people don’t just machine gun their entire bank accounts on it instantly, add a cooldown like they have with selling used cars.
Level 5 weight reduction? 1 hour cooldown before you can buy it again.
Ultra high Turbo or High RPM S Supercharger? 1 hour cooldown.
Engine swap of your choosing? 24hr cooldown.
Titanium Piston & Rods, Camshaft S, Bore/Stroke Up S? 30 min cooldown.
Just a rough idea really.