Ignition is most likely culprit, plugs, wires, cap, etc - engines that run smooth at idle but break down under load again are usually ignition related. Year / model / engine would help determine where to start... I'd be looking into ignition issues.
Shift to a lower gear.
the fuel filter has been changed.
You should probably see about checking out your transmission!
Braking
Whichever is lighter will accelerate more quickly.
bollocks
My truck flutter and temperture gauge drop at the same time
your accelerator is finished (broken)* basically you don't have an accelerate, just two brakes :3
Check motor mounts
Well if you have a carberator on this truck it is most likely the booster pump
The truck has a greater mass and therefore a greater amount of inertia to overcome. To accelerate a greater mass requires a greater force.
gear ratio