Okay so I have been doing a bit of backyard research, and thought I would share...
The fuel filter on the WD21 is a massive unit that takes up quite a bit of under-hood real estate. Agreed?
I needed to change it anyway, and decided to swap in a smaller unit...after some testing....
AutoZone has a whole wall dedicated to PCV and fuel filters. So I grabbed a few and measured flow with a cfm meter and and air hose.
Almost ALL of the filters I checked were within .0002 of being the same flow. Only the very tiny units were more restrictive.
With that being said, I intend on replacing the factory filter with a much smaller clear unit, so I can see when it is dirty.
I assume others have done this, just thought I would throw it out there, since searching revealed nada.