1990 Suburban o2 sensors

Just purchased 1990 Suburban with a 454 and last owner installed headers. Don't see any o2 sensors so maybe they haven't been installed. Can anyone point me to where the computer is and where the o2 sensor harness could be located, and would there be two o2 sensors on that year? Many thanks...

The computer is behind the glove box (need to remove the glove box liner to get at it).

On that year, the 350 only had one O2 in the drivers side exhaust manifold. Not sure about the 454; however, I have the factory manuals at home and can look it up later tonight.

Also, on the 350, the O2 senser wire is purple, will have to see if the 454 is different.

//2000CAYukon

That would be really helpful, I heard the 350s had one but was wondering if the 454 had one or two. I'm hoping the wires are just coiled up and it would be nice to know where to start looking. Maybe on the fire wall but its a bit busy. Thanks very much, Dave... (Also its a 2500)

Factory manual shows only 1 O2 for the 454 and same color wire (purple) on the drivers side.

The Purple wire connects to pin D7 at the ECM.

//2000CAYukon

Great, thank very much, will be checking the puppie out over the weekend.
Sure I'll have more questions, thanks again...