As I have a Van I seem to be limited to either the K&N filter or the Racor that Ford uses.

My K&N is a flat panel filter that fits the original air box.

I haven't found another brand flat panel gauze air filter, nor a Cold Air kit with which I could then mount a conical gauze filter.

With my old pair of 6.5's I had AMS Oil foam filters, AMS doesn't have a foam filter for my van.

Such it is.

I have read in the forum that the gauze filters only make a difference at high air flows.

Iirc, somewhere about 80% of engine design air flow does the OEM Racor filter become restrictive.

The posts, as I recall, said that for daily unload driving stay with the OEM Racor element, and only when loaded down / towing to swap out to the gauze.

Ditto for back-country graded roads, run with the OEM Racor, till you get back to civilization (pavement).