Hey yall I'm new to the forums been reading around a lot after purchasing my 92 firebird. Got it for 400 bucks with 140k on it. Needed a starter and oil pressure sending unit.

I replaced the opsu and now my oil pressure gauge is reading extremely high like needle.off the hash marks high. Is this normal??

Did you get the right sending unit? There are sending units for gauges and different one's for the so called idiot lights.

Yes its the right one. Matched it up with the old one ect. Just reads very high. But after I shut the engine down the gauge drops as it should. Just seems weird to me.

It can't be the right oil pressure unit. The gauge is telling you that the wire that's supposed to have a variable resistance on it at the end (inside the sender) is open (GM gauges pretty much ALWAYS read high when disconnected from their source). Oil pressure senders are only open when faulty, but the switches for idiot lights are always open until the oil pressure drops too low, at which point the switch closes to ground (which would drop off the gauge to 0 PSI/KPa). Either it's the wrong OPS or it's bad.