Victa Powertorque engine, starts no issues, does not idle properly, revs too high when throttle is moved to idle position. I have done the following things, replaced the crankcase 'O' ring, replaced both the carburettor manifold seals, replaced the red diag. spring with the standard one, tried 3 different diaghpragms (if thats how you spell it), added one shim to the throttle slide post, adjusted throttle control, and the poppet valve is set to 'C'. Any ideas on this one people. Assistance greatly appreciated.