Have you even checked fuel pressure?

I assume that you have that goofy, up-side-down secondary fuel filter base with water drain at the bottom. There should be an o-ring fitting at a tee, AFTER the filter that you can measure fuel pressure, before fuel goes into the back of the cyl.  head.

When you say pulling the pump; Do you mean transfer pump, or complete Governor unit?

There are other items that make an engine sluggish.

You need to disassemble and inspect that fuel return check valve, too. There should be a spring, a black sliding valve with an o-ring on it. (this valve causes a restriction, which actually raises the fuel pressure)

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3116 engine_ with goofy upsidedown fuel filter assembly_in paint program.jpg (78KB - 813 downloads)

3116 engine_left side_rightsideup_fuel filter_in paint program.jpg (54KB - 819 downloads)