I installed a bypass filter kit onto my '86 F-250, 6.9L diesel. I installed the unit with the flow coming off the oil gallery in the block, very near the inflow from the oil filter, and the return goes into the oil filler tube on the timing gear cover. The unit comes with a .040 restrictor, which is installed. The oil pressure gauge sender is plumbed into same gallery about 8 inches away. I noticed a small drop on the oil pressure gauge. The gauge is one of those without numbers, but it does read actual pressure but the needle just moves within a ranged denoted "Normal." I would kinda expect to see some drop at idle but but it's lower by about the same amount at all rpms. I have not hooked a second gauge up yet (mostly because I used that easily accessed port for the filter), but based on my previous testing with an external gauge, I think it's dropped by around 5 psi, which would still put it well above the minimum number listed by the engine manufacturer. Any thoughts... Gary.... anyone? Is a slight drop somewhat "normal?"