It will not start, I know the fuel pump is working and it has 60 lbs of pressure?

I have a 2001 silverado v6 2wd, I quit driving it in 05 because the cats were clogged up. It would bog down when driving. So I cut both of them off and test drove it out back and It was fine, besides the obvious of being loud as hell. Anyway I parked it until now without repairing the exhaust. Now it will not start, I know the fuel pump is working and it has 60 lbs of pressure because I drained the gas out of the tank through the valve on the gas line just before it goes into the throttle body. I first drained all the nasty gas that was left in the tank, and kept going once I put the new gas in so I knew it was the good gas. I know its getting gas to the plugs because there wet and gassy when I pull them out to check. I'm getting spark, and there should not be a compression issue cause It was fine when I parked it. Ive tried unplugging the map sensor and trying to start it but it still wont start. What its doing is turning over with no problem, it will fire and sputter barely but not start. I know it does not have the back pressure the it should but it ran fine before I parked it. Ive pulled all the plugs and cleaned them with the same result. It will run for like 5 secs on ether but will stall. So I'm about to the point where I'M just going to start trying everything. I live in Michigan, and I know this is like the worst time of year to do this, but it about time ti fix it. Even though its like 5 degrees out. Any help that anyone can give will be greatly appreciated. Thanks so much.