Toyota pickup power

How oversized are the tires?

Start with the basics - tune up, spark plugs, ignition timing and advance, air filter, vacuum leaks, etc.

Put the standard size tires on it and see if that helps. Larger diameter tires

require more power to turn, but I would thing a 4X4 pickup would not suffer from

a lack of torque.

Also, you may

have been driving faster, but with the oversized tires, you speedometer is wrong. The speedometer uses drive shaft rotations to determine speeed, so it requires a certain diameter tire to be accurate.