Hey, I just got a 1986 GMC Vandura (66,000 miles) from my dad the original owner. This is a U-haul type truck with a 14 foot box on it. It has a 350 V8 and 4.10 rear end set up to pull a trailer. My problem is this, I am not sure about what kind of carb. is on the truck, pretty sure it is a 4 barrel. The choke sticks and it idles very high. This truck has been sitting for a couple of years (5 or so) but it starts great and runs fine but only gets 7 miles to the gallon. I know it has to do with the choke, I changed a vacume hose that was closed coming from a black ball thing mounted on the hood. That seemed to help for a couple weeks but now it is running bad and the choke is sticking again. Real bad backfires and run-on problems. When I start it up it idles high and stays that way, If I take the breather off and stick my finger in the carb and reset the choke it idles nice and quiet, as soon as I give it the gas the choke slaps shut after about 1/4 throttle and stays that way. Any ideas, I am not a mechanic but I do pretend to be one from time to time and I am not totaly helpless. I use this truck everyday as my work truck and drive about 50 miles a day, the gas is killing me! I would LOVE to get 12 MPG or better if it was possable. Thaks in advance, Columbia,SC.