Hey, I put a rebuilt carb on my 250 and now, i'm having a hell of a time with it. In order to have the truck at a decent idle, i've got to have the fuel mixture very rich, which is of course giving me terrible gas mileage, when i adjust it so it is more lean, the truck stalls. The idle screw doesn't do a thing when i turn it, i can drive it all the way in and the truck still runs?? Is this carb garbage???