Hi I had 2 similar problems with my 1995 200hp Johnson several years ago.
One was the Raycor Filter housing had rusted where the filter gasket presses
against the housing. Had to replace the whole assy. About 2 years later the
VRO pump started acting up and turned out to be the Gas side of the pump had
torn and was not pumping very well. At above 2000 rpm it was ok but slower
and at idle I had to pump the fuel bulb to keep it running. Examine the
surface of the filter housing carefully looking for rough surface or bubbles
in the paint where the gasket touches. You can also insert a length of clear
3/8in. house after the bulb to see if you have any bubbles in the fuel while
running.