Engine loses power going up hills

I've taken this thing to the shop for over 8 months now back and forth. 1st Fuel Pump. 2nd. Ignition coil and wires. 3rd. Distributor cap and spark plug wires. 4. Mapf sensor, temperator sensor. 5. Ignition module, and wire harness. 6. Mapf sensor harness was clipped and put back together. 7. Also had to replace the fuel pump again. (Remanufactured that didn't have the psi it needed). All were replaced, except for #6.

Question is: I've lost power. Finally got the vehicle to continually run. But it has no power. If vehicle tries to change gears, you almost litteraly have to take your foot off the gas, but only goes into about 2 gears. If you can get it up to like 35, it will maintain that speed until you hit a downhill slope and then can maintain that speed until the next hill; it then will slow back down to about 25-35 mph. Have any ideas what may be causing this. I've lost all faith in my mechanic, he's had it for over 4-1/2 weeks again.

I didn't seem to have problems with power until this wire was clipped. Could this also be my problem?

Engine Performance problem
2002 Chevy Blazer 6 cyl Four Wheel Drive Automatic

Engine is missing and lacks power. Seems to be worse during warmer days and when air conditioner is on.

Engine performace problems can be caused by many different factors. The first clue may be given by the ECM. If the "check engine" light is on then you should have a code reader plugged in and see why it is on. This may point you in the right direction. However there are a few things you can check that are pretty quick and painless. 1 - make sure air filter is clean and not clogged, 2 - check plug gap, 3 - check plug wires for arcs. Based on the limited information you provided I would start with these and go from there. Some of the more complex problems it may be is a bad fuel injector, bad O2 sensors, engine wear. I hope this helps!