Ok, let'* take care of the important thing first. Oil, in an engine, is like the life blood of the human body. No flow, no life.
So, you have a L67 supercharged engine. 5W-30 oil. Oil pressure jumping. I'd like more clarification on that because the gauge will do 1 of 2 things. 1. Not work. 2 Work. Now, when I say work, I mean, it will ACTUALLY tell you when your oil is hot and when the oil is losing its viscosity and when the oil is brand new.
Do you know the complete history of the car? If the previous owner didn't tell you at LEAST when the last oil change was done, go get it done now. Then come back and tell us what the OP gauge is doing.
1997 Pontiac Bonneville SEi-SCRAPYARD
2000 Chevrolet Blazer LT 4X4 4.3L
2002 Chevrolet *-10 LS Ext Cab 4X4 5.7 V8