i need help. i live in denver so 5,280 ft elevation. pilot jet 60 and main is 148. motor has pod filter and expansion pipe with silencer not full lenght exhaust. starts and idles fine but when throotle is opened it starts popping acting like its starving for fuel or running to rich.it will not hit powerband . does this motor have a power valve. please email me soxx4u@yahoo.com.