Hi all, Suffering abysmal fuel economy (10 mpg) from a nasty 2 bl Holley.. list number 2011 if I remember correctly.. I know the mixture screws only affect idle, so can anyone advise what I need to change (and to what sizes) to be about right on mixture?

Doesn't need to be precise, but the right ball-park would be better than the sooty plugs I got now!

(I don't want to do my service while an over-rich mixture is making everything filthy!)

Thanks, Andy.