I have a 1985 ford f-150 explorer pick up 4.9 300 6 that I just got done converting to a 4wd 4speed. Now when I start the truck the engine idles so high that it sounds like it is going to blow up. The only time it slows is when it is in gear or if i let the clutch almost all the way out. Had the carb rebuilt but not sure if it was done right. If I push the butterfly down alittle when engine is running it also slows alittle and sounds about right but shakes real bad. Turned the idle screw down but no improvement. I could really use some advice. Thank all of you that help on this forum.