When I am hauling a heavy load, if I put the pedal down the acceleration is just not there, especially on grades. If I have it on cruise control, it will backshift and accelerate like crazy. I have replaced the fuel filter and cleaned and reoiled (not over oiled) the K&N air filter and no improvement. Dealer gets no codes when they plug it in. Any suggestions? :confused:

You can try cleaning the MAP sensor. I dont know if that will help or not but its worth a try.

drew, I had a problem that sound just about what you are describing. After many trips to the dealer we found that the throttle positioning switch was not getting full voltage to open the throttle all the way. this condition will not throw a code, so have the dealer to look for low voltage. Hope this will help you, good luck.