[Cameron Koehn]

I checked and there is no modification for 90% oil filter.

Follow my logic. If the pump pumps oil when I turn it by hand, and the cam and gear turn when I hold them with a wrench and turn the crank, and the pump gears have not appeared to spin on pump shaft, and the oil pickup is stock with no pinholes, ...oh maybe the bypass is opening at a super low pressure so that when I turn by hand I get flow, but when installed and pumping against pressure, it bypasses?