"bucking" Bronco Ii

I recently purchased a 1986 Bronco II. It has a 2.9 fuel injected 2.9 V6 engine. It has new spark plugs(gapped at 44 thou) new plug wires, new distributer cap, new battery, starter, solonoid. I have also replaced the intank fuel pump, the fuel filter and verified that the AUX pump is operational. I have also checked for and repaired any vacuum leaks that I could find.Having said this, the vehicle starts fine, but seems to "Hunt" at idle (revs up idles back over and over). At highway speed it runs OK, if I get off road and put the truck in low 4WD and first gear it bucks, jerks,and I do believe that if I did not push in the clutch, it would throw me through the windshield. HELP!!

I would look at the throttle position sensor. Check if it came loose or is bad.