Cylinder 4 misfire

[mtnvol1]

Got a problem. Recently, my 'check engine' light came on. It came on when I was coming up the mountain where I live. I had it checked and it showed a cylinder 4 misfire. I've got 115000 miles on the truck. It's a '98 Z71 with a 5.7 Vortec. What I have done is replaced the plugs, plug wires, distributor cap and rotor, and put in a new fuel filter. I had the code cleared. However, I am still getting the same misfire code when the engine is under a steady load, like going up a long hill. A mechanic has been looking at it but has not found anything wrong. Also, I did do a compression check on cylinder 4 and the compression was fine. Is there something else I can check?

[Jeremy WI]

Have the mechanic hook up the scantool and look at the cam retard value, it should be 0 degrees. It might be a leaking injector, but that should cause a misfire at idle almost as well