OK, so I have look through the forums and I haven't seen a dash board plug schematic for a 1990 Camaro RS.
I have a complete set of Autometer Gauges and had someone else do the initial wiring. It's a hack job at best.
I have a water temp gauge that doesn't work at all. I think I have a solution for that with just a change of the sensor in the head.
I think to the oil pressure gauge also needs the correct sending unit but I need to do some additional plumbing to allow both the old sending unit and the new Autometer sending unit to exist as the fuel pump shut off will not work with the new Autometer sending unit.

Can anyone confirm the wiring plug layout for a 1990. I have a layout for 1991 and 1992 but not sure if they are the same.

Thanks.

 

I have a 1990 CSM so you're in luck. I took pics of the relevant pages:

 

Just one last question? if the SES indicator is set by a ground from the ECM, where is that ground pin? CA wants to see a SES light go on and off when the engine is off and when it is running. Pain in the a$% but that's what the referee want to see. From my understanding the SES gets power 12v and is an open circuit until the ECM send a ground which lights the indicator. Just want to make sure I have the last piece ready to go.

 

It appears it is the BRN/WHT wire from the ECM: