Robert Cozzens

Hello I have a 96 GMC sanoma 4.3 4wd automatic. Here's my problem the code pops as a random cylinder misfire. But doesn't run like a misfire. It has super low power but doesn't miss. I have to floor of to get to 25. I have replaced plugs, wires, cap, rotor and coil but still nothing. It does have a screw broke off of distributor cap but have it sinched down and when I mess with the cap it has no change in power. I have also hollowed out the cat thinking it was plugged please help