mariop

I have a very good 1998 Chevy K1500 4wd truck that hasn't given me a hint of a problem. It has 240,000 miles on it and had a leaking intake gasket for years. Radiator ran low all the time but it never overheated. I thought I'd change the intake gasket and do something nice for my trusty steed. I should have left it alone . Now the truck won't run correctly and misfires like crazy. The codes I originally got were P0300 (random multiple missfires) and P1345 (manufacturer control). I thought a drive may help and the code changed to P0301 (misfire #1 cylinder) and the 1345 went away. At this point I changed the distributor and I now have only the 1345 code and it is still misfiring and runs like crap. I'll lay out what I've done so far.

Change intake gasket.
Install new cap, rotor, plugs ran like crap.

checked fuel pressure, its good
backtracked all of the work I did back down to the gasket.
Carefully checked all electrical connections to make sure no bent prongs.
Installed another intake gasket thinking I messed something, put her all back together, no change.

checked for vacuum leaks and inspected plastic plenum.
Tried the old cap rotor and wires in case new stuff was bad (wasn't).
bought and reinstalled another new cap, rotor and wires (same new wires).
Installed new distributor.

I am getting ready to change the injectors, there isn't anything left. Anyone have an idea of whats going on? I don't know how the injectors could go bad during a gasket change.