i dont think there is really a "maximum" power for a car... but having said that i am sure there are certain limitations depending upon what brakes you run.. the structural integrity of the car etc etc.... engineers would know all the bits and pieces to upgrade etc..
there are plenty of beetles out there with 2.0T motors from subaru... and they would be in the 160kW range if they are stock.
see.... air and water do mix 😉
1974 1300
1997 MK3 Golf GL
2003 NB Cabrio
2012 Golf VI GTI
2014 Audi A4 Quattro