I don't know which diesels don't accelerate very well, or don't down shift when you "floor" the accelerator pedal, but mine is no slouch. Which large gasser Class A outperforms mine, when moving 35,000 lbs? Mine does just fine, and all I have to do is jam the pedal to the floor, and the 6-speed Allison automatically selects the optimum gear ratio(for highest performance). The trick is to HOLD the pedal all the way down as long as it takes to satisfy your performance needs (reach your cruise speed as quickly as possible).