Ok let's see where to start...1989 22re 4x4 truck ran great and then just started having little to no power especially on hills.

Recent tuneup with new plugs and wires, oil change w/filter, air filter, induction service, tested vac lines and fuel pressure, new fuel filter and coil(6 months/3,000 miles ago)

Throws a code for the knock sensor which was replaced with a new OEM. KS cable to ECU tests OK, and ECU looks OK inside (no burns etc...)

Truck idles fine and runs good except for loss of power and fuel consumption seems high. Revs fine in thwe driveway with no load. Just no power under load.

Don't know where else to look.