I believe the thermactor bumps you removed help to measure exhaust gas? I removed them on my GT40s, I had heard you can gain a few horsepower just from removing them. Like they said, you really need to port match your intake gasket, and even the upper gasket. From my understanding, you really gain power from porting in the bowl/combustion chamber. Smoothness and shape determine how much. You want a 'tear drop' shape, which help the fuel combuster more efficiently. Unless you have alot of experience in porting, or have some trash heads, you might want to leave this part to the pros, if you hit your valve seat or don't shape it properly, they're trashed anyways. Good luck!