I Live Here
Joined: Mar 2004
Location: Denver, Colorado
Not really sure what that could mean. The sending unit may have been partially blocked before and is now reading correctly. I'm not familiar with the Z32 oil pressure guages and sending units, maybe Spongerider can provide an answer here. I know with my Z31, the pressures were all over the place as yours are. With the weight of oil I was running, 15W40, I'd see pressures as high as 60 psi at idle when cold, dropping off to 15 psi at idle at full temperature. The unit never failed, so I imagine that's what it was supposed to be reading.
If your oil has been in the engine for a while and seen any extreme temperatures, maybe it's time for a change. Oil can sheer down to a lower weight after a while, you may be seeing the effects of this through the guage.
1992 Yamaha FZR 1000. 145 Hp, all stock..