Mr Hintz, There really isn't any lint filtration system on this style of washer. The only other place to check for build up of lint is in the tub drain line, drain pump and drain hose. Interestingly with this type of whirlpool product when the machine is agitating the pump is spinning backwards pulling in air thru the drain line. If there is a small clog of lint debris in the lines or pump, it may be working back into the tub. Other than that if you've cleaned the plastic tub when you had the agitator drum out that's about all you can do.

Those plugs are a catch for lint yes, however not like a re-circulation filter system or screen found in much older models that are cleaned out after each use. That's what I thought you were referring to.
These plugs are located under the agitator, in the inner tub. If the prongs are worn then replace them with new plugs and have the prongs facing away from center. I'm not sure how effective they are, seeing the amount of lint found in most dryers and vents but give it a shot.