Help For about two months I have been having a problem with my 2005 Silverado. The truck is a K3500 extended cab non dually LT truck with a 5 speed allison. After the engine is warmed up to the operating temp. I can not seem to exceed 2000 rpm. As I advance the accelerator I start to lose rpm ,the transmission will down shift ,the rpm will momentarily increase as I continue to slow. When the rpm drops below 2000 the power will return and begin to accelerate again. It does not do this all the time but I get no warning when it will. Once I back off on the accelerator and allow the rpm to decrease I seem to have the power back. If any one out there can help I would appreciate it Thank you........ Alf.