Dropped RPMS

I fear it's another epidemic, contagious poor thoughts beyond factory specs to about every engine builder.
It will never be found in any factory manual explaining a fine filter first.
Even here in the swamps, at the stills, we understand course filters first.

I did find that DDC secondary cartridge (filters that go into the metal housing) factory spec; 22 mic.
The finest factory secondary (spin on) filter is around 10 mic.

Old Detroits flow lots of fuel.
Old Detroits can near burn anything other than water.
High performance 6-71 would luv great fuel but what ever you are burning, it needs a lot of it flowing.

But I have been drawn into a side topic and digressed.

Please check the blower bypass hoses and install a pressure gauge on the last filter output rite before the engine.

That's not to bad but a great start.
Send a pic of the media (filter).

I use Paint to quickly downsize photos to less than 650 pix on my desktop.

Have you been running bio-cide to keep fuel clean? Once it gets algee may need to have fuel and tanks cleaned?