I cleaned the fuel filter.
Most junk was around the small metal screen on the intake side, even though this stuff looks like is fine enough to pass that screen. I guess due to the diagonal installation position, the stuff slowly drips off the main filter screen and collects on these edges.
Another shot of the intake side
Exit side looks clean, except...
For these particles under the O-ring. So apparently these particles are small enough to pass the filter.
I soaked the filter screen in paint thinner & rinsed it under running water, but I didn't see any dirt coming off it.
All assembled, including the pipe fittings