2002 Chevy S-10 no power up hills

Engine Performance problem
2002 Chevy S-10 6 cyl Four Wheel Drive Automatic

Basically when Going up hills I notice it the most. It drops down a gear and the rpms try to come up but there is no power. I changed the fuel filter. And gave it the full tune up. Plugs wires cap and rotor. None of this helps. When it drops down a gear and the rpms are up it makes a crackle sound. Basically if its not spark or fuel I have no idea what could cause this. Do you have any ideas.