Chainsaw Repair

To answer your question about the step in the exhaust port.   Yes I did taper mine, but I did not raise the port.   That will drop compression, lose torque, and raise rpm,   

The point of widening the ports is to increase flow through the engine.   If the exhaust flows out better then it will also allow the incoming fuel air mixture to increase.

  In reality I think anytime you make any changes to these engines that helps to increase the HP rating there is also going to be a small increase in RPM.