I have been chasing an engine vibration in my 05 4x4 6spd H.O. short bed quad cab for about 6 months. It varies but most noticeable at 2,000 to 2,400 rpm and at idle. Truck has 135K on it. I tow a 6 ton equipment trailer and plow with it.
Had an injector coil fail around 90K and replaced that...