fd oil pressure question?
 

I have been noticing a dip in oil pressure at idle latley on my fd. Tested oil pressure today with another gauge, the sending unit is deffinatly off and slow to respond so I ordered a new one today. But i'm also noticing at idle my oil pressure is showing a bit lower, about 20psi. Im not sure what normal idle oil pressure is on the fd's, I did a search and came up with nothing on here. Mazda says 50psi at 3k. I'm well in spec with that number, possibly eshaft thermal bypass valve, or is 20ish around idle normal? Thanks for any thoughts guys, Kyle