RE: Whats Wrong?
I would still check the head. did you make sure the gasket(s) where moved to the new head? It could be a hole in your line coming from the tank to the engine. A hole from the muffler to the tank would cause a slight rise in idle speed due to reduced fuel line pressure. And to check your o ring on the high speed needle, you need to remove the needle by turning it counter clockwise until it wont back out any more. Then grab it with your finger or pliers and pull it out. Check the o ring for wear, is it stretched, cracked, missing? You could just replace it to make sure, O rings are like ten cents a piece. Hope this helps.