[TitaniumTT]

Shimming the bypass with an FD reg is only going to keep the bypass from dumping oil when the pressure gets too high. Shimming the reg brings the point where the bypass will bypass higher, it does nothing for lower pressures. Plus, FWIW, I am dropping my oil pan front cover this weekend to replace a squeezed out o-ring, I think my front cover is warped as this is the second time it's happened, and I am pulling my shims OUT. I have seen upwards of 125psi oil pressure and that's just way to high. It doesn't need to be there and is doing more damage than good in my eyes.

While your pressure is low, it's enough to raise an eyebrow but noting out of the ordinary. Did you modify any of the oil passages? Are you sure the OP was within spec? They may LOOK good, but the tolerances on them are so eff'ing tight that just a little wear will show low pressure. My pump was out of spec but it was only by a few thou, and I was in a pinch so I tossed it in... My pressure does the same thing as yours down low. When I pull my front cover I'm going to play musical oil pump parts to see if I can get a pump that falls within spec. I have like a dozen pumps but only one with the o-ring groove machined in it.

Sadly, the only thing to do is pull the front cover BUT I don't think you're at that point. I would honestly just wait and see what the bump in viscosity does. A new oil pump might be in order. Did you clean up any of the passages?