I agree with most of what Beater said ,I'd also look very closely at the inside of the cap and the rotor for cracks Or Cross arching in the cap. I think a lean out would more at the higher rpm then at low. You can check the carb for dirt as you may think it being a issue, it can't hurt to look. You may also want to check the Valve lash. With the Up grade on the cam their could be???? a slit chance your pulling on the press in studs and loosing valve adjustment?? If you did not change over to screw in studs.
God doesn't like ugly.
