1998 c1500 4.3 misfire troubles

[straight6chevyguy]

Hello everyone I have been having trouble again with my 98 c1500 misfiring/running poorly and I'm a bit stumped.

The truck is a 1998 c1500 4.3 v6 5 speed manual 2wd. with 163K on the od

So my problem is: Engine Idles a little rough and has what seems like a misfire.
Misfiring is worse or more noticeable at what I would call lite load higher rpm conditions. Like 1800 2k-2500 rang while shifting through the gears under lite load conditions and also driving at cruising speeds.

The condition is worse in damp wet weather.

The condition is like a time I had a bad dis. cap.

I have tried Three (3) different dis. caps, one that I had been using, one almost new and one brand new cap.

rotor button looks good.

Plug wires are not very old and test good with a ohm meter

Swapped around spark plugs one cylinder at a time with a good but used spark plug.

Brand new Ignition coil (original went bad June of last year)

Pretty new ICM (Replaced a year or so ago)

I have tried a different ignition coil and Icm from anther truck.

TPS sensor tests good.

I only had trouble codes for EVAP
I drove the truck a for a MONTH like this and had NO MISFIRE CODES I checked several times and then gave up and did not check for a couple months and drove the truck like it is (mostly just to work and back) (12 miles to and 12 miles back 5 days a week)

I Recently checked again and I had a code for a misfire on cylinder no.4
I changed out cylinder no. 4 wire just because. I thought at first it may have ran better but was wrong.

In my opinion it seems like multiple cylinders misfiring but I can not be 100% sure.

Fuel pressure is close to 60psi ignition on engine not running.
With engine running its just above 50psi. If my memory is correct the pressure is good?

Other then doing a compression check I'm not really sure what next to check so I'm hoping some of you out there have suggestions!