When I first start up and try to drive home the truck will bog down so bad it will hardly move and backfire like crazy, part throttle or floored or anywhere in between. After a few minutes though it gets a little better. Also, the high end (4,000 and up) pulls pretty hard but the low end is hardly ever there.
About the only time I have low end is after a highway ride, right after. I checked the fuel system, it gets 55-65 psi, gutted the cats and removed the EGR (and had Virgil tune for it), replaced everything ignition, replaced intake gaskets, and checked the coolant temp sensor. No improvement. As I was watching the oil pressure gauge, I noticed that it seems to do better while the oil pressure is up. Could it be bad lifters maybe? I dont know much about them but I do know they are supposed to pump up.
The truck has ~140,000 miles. Running Mobil 1 and a quart of Lucas. V says the front O2 sensors max out under full throttle but not sure why.