[suburban99]

Originally Posted by roundhouse

use a remote gauge, or a flex hose and duct tape it to the windshield so you can see it while youre driving, but its not inside the cab.

also, try driving it with the O2 sensors unplugged, so it will stay in open loop,

it will throw a code but give it a try,

I have a 91 Mustang EFI in my 73 Bronco, and I somehow got the O2 sensors cross wired. and it would do exactly what youre describing.
I drove it with them unplugged for months because It never occured to me that they were crossed.
and it drove fine with them unplugged and staying in open loop

I had the left o2 wire plugged into the right side sensor and the right side plugged into the left sensor.

and that makes the computer go crazy trying to keep adding more and more fuel and then less and less fuel
in a normal vehicle this is not possible since the wires wont reach, however in a transplant it is easy to do.

Yeah that would be easy to do... since I repinned my own harness...but I had a bank 1 Sensor 1 error...changed that O2 sensor and code went away.