Chevrolet Repair: 1993 Chevrolet Motor, catalytic convertor, chevrolet motor

Question
My 93 Chevy pickup has lost a lot of its power.  We have replaced the fuel filter, spark plugs and wires, and the o2 sensor.  It helped the motor, but it still bogs down in high RPMs.  We rebuilt the throttle body not too long ago as well.  The motor just does not act right when the transmission has to down shit to go up a hill, and it only bogs down.  It also makes a funny humming noise when it does this as well.

Answer
It possibly can be fuel related.- weak fuel pressure. Monitor fuel pressure while driving under a load. Make sure pressure is over 10psi.

A clogged catalytic convertor will also cause these symptoms.

Make sure both fuel injectors are spraying a good pattern. One of the injectors could be inop or intermittently cutting out.