Tell me why I can't use the new Fuchs?
 

I have an 06 997 S with 19" wheels, why do the new Fuchs only fit the turbo, 4 and 4S? They are 19" right?

must be different "offsets". Depending on the offsets, the wheel may sit too far "out" or towards the fender lip. In a "narrow car" they likely hit the fender lip.

If you look at the wheels part #, you will see an "ET". this is german abreviation for offset. If the wheels are the same sizes, but the ETs aren't the same, the wheels will sit differently on the car.