I have a 90 rs where do I start looking?

 

The ecm should be in the passenger side dash.

 

Remove the black plastic panel just above the passenger's feet and you'll see a huge wireloom coming up into the dash. The ECU is there, close to the A-pillar, right behind the plastic of the dashboard. Better lie on your back with a flashlight pointed up there because there is a plastic tab that holds the ECU in a plastic cradle.

Hope this helps.
Lou

 

Thanks i found it.