>>>*The good sign here is the lack of any noises, and the fact that you know oil is moving on the top end.

Any lack of oil volume normally lets you know fairly quickly.

The oil pump and oiling systems on these engines are almost fail proof, the pump will push oil even when nearly completely worn out.

Low idle pressure that recovers quickly with RPM is nearly always related to more than normal main bearing clearence or the bypass, I would hazard a guess that an oil pump failure concern in this situation just doesn't happen.

What CAN happen is the bypass valve sticks open, (the usual dirt/debris/swarf, etc)this will cause lower than normal idle pressure yet quick recovery with RPM increases.

She will likely run just fine that way for the rest of her life but it makes a person nervous.

Of course you want to be sure before you hear the loud noise and see the big cloud of smoke. And then go, "OH! That's what that was!"......

Best to get a remote gauge on there and check, one of Toyota's weak links is the gauges, I have seen lots of those that just don't work real well....*EB