1) RS, LS, and GS all have the same motor, a b18b1 which has 140 hp and 126 ft-lbs trq.The GSR has a b18c1 with 170hp and 127 ft-lbs trq.The type-R has a b18c5 with 195hp and 128 ft-lbs trq.2) a GSR would be better for everyday use as a type-R would be more likely to be stolen.3) No, adding a turbo to a car that has vtec will not be unstable. It will just have to be tuned differently.4) PSI= Pounds per Square InchRPM= Revolutions Per Minute, which is the speed the motor rotates at.Hope that helps you =]