need help with CEL for both 02 sensor after replacing 02 sensors.

[steamboatnsx]

I will try to make this as brief as possible.
My 1991 has had a CEL light on for a little while code 1 and 2, front and rear 02 sensors. It always fine until after driving for a hour one day I restarted it a few minutes later and it was down on power by almost 50% and a slight stutter.
So I replace both 02 sensors, still down on power. I check all the coil packs they are reading 1.2 but see that one coil pack is missing a bolt holding it in.
I replace missing bolt and it runs great back to full power but was showing CEL for front 02 sensor, and now CEL for both 02 sensors.
Why am I still getting CEL for both 02 sensors even though I just replaced them?
PS I have been pulling the clock fuse to reset ECU several time including after replacing missing bolt from coil pack.

Thanks for any advice

 

[Briank]

Do you have headers?

 

[steamboatnsx]

No headers, the only mods are the larger air intake scoop (no cold air intake) and short gears.

 

[ftuhy]

I have a '96 (4 sensors), and I don't quite remember the wiring paths for '91 sensors (2 sensors, I believe). But, is it possible you wired them such that you swapped the connectors? I'm don't know if sensor cable lengths would make a swap possible, but that would confuse the computer.

 

[steamboatnsx]

I had a shop install the 02 sensors but I think the wires are supposed to be a different length although I think the part number for the two sensors were the same.