1998 Chevrolet Cheyenne Cranks but will not start

I just got this truck and it ran fine it had the slightest miss to it. Until about a week after driving it the check engine light came on so I put it on a computer and it said it was the cam and crank shaft position sensors.I replaced both sensors. SO I went out to start it one day and as soon as it started it died so I started it back and gave it gas the engine had a real bad jerky shake to it and as I was giving it gas the rpms would hardly move it took it awhile for them to get back up. As I would repeat this process atleast 3 times it would idle fine and drive awesome.I noticed after awhile the problem got worse and the truck would automatically die after driving especially if I did not hold the gas down and the check engine light came back on and it said it was the camshaft position sensor only this time it only read one of them so I replaced it and the check engine light went off and now the car will not start at all it will crank but not start the catlytic converter was cherry red so I knocked all the honeycomb out of it. I replaced the plugs, wires, distrubutor cap, air filter and still nothing any help at all would be appreciated thanks so much.