2 more things I would check one being the float in the carb or the Idle screw and two the PCV valve I had a simallar problem it happen when I push the clutch in. If you need a stock Carb I do have one I'll let it go for $30 plus Shipping costs it need a rebuild but it worked about 2 months ago. Oh and good luck do you have a hayes or chilton book for the truck? <img src="/forums/images/graemlins/kewl.gif" alt="" />