1997 Chevy Suburban 97 Suburban 5.7L boggs down

My suburban boggs down severly when driving and when reving in park or neutral. I have done multiple things to correct this problem to include, new plugs, plug wires, distributor cap and rotor, new spider injector, compression test, fuel pressure test, and finally dissabled the cats to see if they were plugged up. I also checked for vacuum leaks with propane and found none. The plugs are sparking fine and the gaps are good, however, I keep getting a number 6 cylinder misfire code and a left bank oxygen sensor code. That oxygen sensor was replace about a month ago. It started out gradual but has progressed to the point where it is near impossible to make it up a hill. Any one have a clue what else to try? Any suggestions would be greatly appriciated.