[grey88gt]

Maybe this will help. When ever you increase load or open the throttle, manifold vacuum will decrease until the load is mantained or goes away. When you take off or want to go faster you decrease manifold vacuum. If you have say a 6.5 " power valve in your carb, the vacuum has to drop to that point before the power valve will open thus enriching the fuel . So the bigger the number on the power valve the sooner it will open and the longer it will stay open thus using more gas. You might try droping a jet size or so. The jet you have is 62 and the extra 2 at the end I do belive is the grade or quality of the jet (someone correct me if Iam wrong ) . I think I saw a post on here , where someone explained that. I still dont a 62 jet is big enough for your mpg to be that low.