I first noticed the low fuel economy and major loss of power in a rainstorm. It acted like the choke was on. Black smoke emanated from the exhaust. Examining the air filter showed that there was water pooled in the housing in the depression surrounding the filter, and the paper element was soggy. The ram air hose (which has since been replaced with clothes dryer hose) channels water in during a storm and saturates the paper air filter element. Without the intake hose, water is thrown up from the wheels and passing cars that is sucked into the air cleaner housing, plus driving rain passing through the grill.

I did not see any real danger from the water getting into the engine, and this was an exceptional storm. The point is though, that water CAN enter the intake at times.

Since then, I noticed the paper element would also get soggy during very damp or misty days greatly restricting air flow.

After much head scratching, I bought a $22 electrostatic filter from Ace hardware designed for home furnaces. An old Fram filter from my car was stripped out to just the two big rubber rings and the mesh inner ring, so that what I was left with resembled a spool.

Other sources include:
Riteair
Lifetimeelectrostaticfilter

MAX from Riteair

They claim to remove 97% of particles, and even 95% of bacteria, but there is a companion spray to make the element stickier at $5. You can used Pam cooking spray.

The new furnace filter was disassembled and the plastic elements cut into strips to fit the original Fram filter. I wound the new strips on this form maintaining the original order of materials in hopes it would still have the electrostatic filtering properties.

Edges of the new filter element were sealed with acrylic or latex caulk.

After one year of use.

The difference in fuel consumption was immediately noticeable, and the losses on rainy and muggy days are gone.

I examine the new filter periodically, and rinse it with a garden hose if it needs it. It has been over a year, and so far the filter looks almost as it did when I built it, except the caulk has turned brownish.

The newer rectangular filters should be a snap to make.

Update  It turns out my engine loves water injection; it just doens't like soggy air filters.

HHO generator

PCV Filter Trap