I drive a 1987 CRX with a D15A2 engine. The stock carb has been replaced with a Weber 32/36 DGEV. Set up for SCCA ITC class, the engine is basically stock. What simple changes can be made to increase horsepower and torque? Reading about various engines, the D15A3 is said to produce ~50% more hp and the only difference seems to be the head. Can I get at least some of this power increase by swapping to a D15A3 head? Can I continue to use my current Weber induction on the D15A3 head.