chevy silverado missfire

i have a 1998 chevy silverado, my problem is that it dumps gas out number 3 cylinder, it shows a code of po303 missfire, i have changed plugs and wires, i have put new fuel pressure regulator on, i have put new pick up in distributor, i have done everything except change the pcm, the dealer says it's not that but i think it is, can anyone tell what i might have missed or do i need a new pcm.

thanks cliff

my problem is that it dumps gas out number 3 cylinder

i assume it has a dead miss? spark at 3? if so look at the schematic and back probe the connector on the intake for a pulsing ground at 3 injector. if it checks good you could replace it . have you run a compession test?

Make shure your intake manifold gasket is good. Chevy had trouble with the later vortec 350`s .