Thanks, Al.
I think the screen is clean.

When I put the new manifold and gasket on, I checked to be sure that was lined up (or at least I knew to do it)

What do you think about an air leak somewhere?

I do see a few air bubbles in the carb side of the primer while it's running.
Maybe the new hoses need heated so they shrink better around the fittings?
My 22 yo son is doing some of the work and he sometimes may want to cut a corner or two