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 thanks

 

Far too many harness changes necessary to even begin creating a list. I so strongly recommend having someone rework your 1990 TBI harness for TPI. Years ago I used to do this, but don't have the time for this sort of project anymore. Check with TPI Parts (http://www.tpiparts.net) because I think they used to offer this rework service.

This may appear to be an odd way of going about it, but very seriously, it is the smoothest transition. I promise.

 

'88 harness will not work on a '90.

 

this harness is already in. there is no going back. There is a way to make this harness work it is completely installed. I need some guidance a little different then "dont use the harness"

 

Compare the 1990 TBI wiring diagrams to the 1988 TPI wiring diagrams and make any necessary changes at C207 and C100. After turning the key, identify what doesn't work and spend more time in the service manual.

While the 1990 harness is out, that would be an excellent opportunity to modify it for TPI and then change engine harness. I've changed an engine harness with motor in the car.