Can you tell from a spark plug if the cylinder is lacking fuel or spark? The motor the pictured spark plug came from is a 2002 4.3 mpi that's is down on RPMs from where it should be at. This is cylinder number 3 plug and looks like it is hardly firing, all other plugs look like they are firing fine. All plugs were new at the beginning of the season and have about 40 hours on them. One side of the spark plug strap does have some carbon build up on it, so it has to be at least firing a little bit.

Cap, rotor, distributor, and plugs were all new at the beginning of the season. Plug wires were not replaced.

Compression on all 6 cylinders 150-155psi

New fuel water separator, and fuel pressure steady at 40 psi, even under load with lack of RPM.

Planning on new spark plug wires and having the injectors cleaned, but now as I'm typing this I'm wondering if potentially the exhaust manifold is leaking water in that cylinder and that's why the plug looks so clean??

Cylinder number 1 plug for reference

Looks like that cylinder isn’t firing at all. Change that plug wire

Check your injector(s). There is no fuel to that cylinder.

Hook the plug up to the boot and turn the motor over with the plug grounded. I bet it sparks.

If eng was just ran, plug should be wet if fuel is OK but no spark. Wait too long and wet plug will dry out.

get you an inline spark tester. $10 or so at Autozone or wherever.. looks brand new as in never been fired. I'm guessing you have spark issues. probably a plug wire, ground issue, whatever.
one time i had a plug wire get old and worn and it was arcing through the shielding onto the engine and causing that cylinder to misfire. i'm surprised you don't notice a significant misfire if you have a spark issue.

Did this just start this season?
Saying last season it was fine, or this just started so the parts were replaced to try and fix?