Have you tuned the ignition and carb? That .509 is going to have zero vacuum. I'd bet the power valve is open at idle messing everything else up except when it's cold and needs the fuel.

Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.