ok so I am installing an 89 TPI system using an 88 TPI Harness in my 90 TBI camaro. I was told that even though the harness will plug into the firewall with no problems there will be some problems with things working because the circuits could be different. And I will need to pinout something. IS this true and what is a Pinout

 

A pinout is a "plan" for want of a better word that shows what wires go where.
Here is ECM pinout for '165 ECM used in '86 - '89 TPI cars
http://www.chevythunder.com/198689_f...dy_1227165.htm

Also good to compare the engine wiring differences between the two setups
88 TPI
http://www.austinthirdgen.org/mkport...ine_wiring.gif
'90 TBI
http://www.austinthirdgen.org/mkport...ine_wiring.gif

 

these diagrams are for the ECM right?. i was lookin for where it goes into the firewall on the drivers side.

There would be no problems with plugging an 89 ECM into an 88 Harness on the pass side right?

 

86-89 ECMs are interchangeable