Skysurfer, when you say you have the low speed as lean as you can get it, do you mean you have the low speed needle all the way in or all the way out? You may or may not know this but the low speed needle adjustment is reverse of the high speed needle (and most others for that matter) where it is richer turning in and leaner turning out. You may already know this and if you do I appologise, just FYI. Also maybe try turning the regulator in a bit (1/4 turns at a time). This may also help the idle mixture.

Brian