Fuel Filter/Pressure Issue

OK, forced pressurized air through the vent line, and made a minor adjustment to accelerator pump linkage. I drove the car for 20 minutes and when I stopped/shut down to check the filter it was completely full. I let it set for over an hour and it remained full.

Then I drove the car again, shut down and within 45 minutes the filter was half full.

I'm stumped.

Thanks all.