My Bronco with 5.0 liter engine is having some acceleration problems. It has hesitation and bucking problems just above minimal throttle position. If I am driving along at any speed at the most economical throttle setting is is smooth, but when I accelerate it bucks uncomfortably. If I push on past an bucking it has good power and runs smoothly. I thought it might be the MAP or TPS, I changed them both with no change in performance. It has no trouble codes and I am not sure what to do next. Thank You in advance for your time.