i am having simaliar problems with my truck but mine at 35 - 40 mph the rpms will go up and down and when i accelerate the rpms go up about 200 rpms and then jump down almost 5-6 hundred like it found another gear ive replaced the apps once throught the dealer and that one lasted a year so i found a used one that was still in good working order (tried on friends truck first) and still having same problem. could it be transmission or apps or something else? when i replaced the apps the first time the problem went away. i have also replaced the factory lift pump with a fass 95/150 and replaced my vp44