105k miles. truck bogs as if losing cylinders under load (going uphill without downshifting). no problems if you downshift and keep rpms over 3000. once you top the hill, you can feel the cylinder(s) fire again. new plugs, wires, cap, rotor, air filter, fuel filter, O2 sensors, 35psi fuel pressure at pump, only trouble code (comes on every now and then even though problem is constant) reads "multiple cylinder misfire". 1,3 or 5 injector disconnect drops idle 100 rpm. 2,4 or 6 injector disconnect drops idle only 20 rpm. dealer flushed injectors. $600.00 later...dealer says "i don't know". any ideas?

oops...stock tires and gears, 5spd., reg. gas, no knocking, no pinging, slightly rough idle.