best air cleaner to use?

I had an excellent seal, wheel bearing grease on the filter element's sealing surfaces with true and flat filter housing flanges, and a rubber washer under the wing nut. Was the type of filter assembly that fits into a 3" ID rubber hose with a hose clamp on it. The grit could have only gone thru the filter element.

Agreed, it can only get better from where the OP is at. Just a question of what is desired as to how much better it can get.