I have a 1987 iroc-z i dropped in a 383 carburated motor i recently went back to using the stock gauges and the oil pressure gauge doesnt work correctly. when i put the hey in it pings up past 60 psi and as i rev the motor it lowers down as if working backwards....I found the tan wire and its connected to the oil psi sending unit from my aftemarket gauge can this be the problem?? Do i need to use a OEM sending unit or is there a wire i dont have grounded.....I cut all the wires think i wouldnt need them so im kinda stuck cause i dont know what they all go to...Please help

 

A stock gauge needs a stock sending unit.

 

Do I also need to have the terminal above the oil filter hooked up and plugged in and if so do you know which wires those are cause i cut all the small wires coming from the drivers side firewall....Thanks