Is this a bad MOD

[CobraMountaineer]

I just bought a 1998 Mountaineer, and it has a V8 302. I though it was stock, until I started it up. 2 owners before me, put a 1994 Mustang GT Cobra engine in it. Now, I understand the OBD situation, but he got it in there, and it works. I have a few questions.
I am getting an AIRB and an AIRD circut failure. Any ideas?

Under a load/hard acceleration the valve train rattles like a diesel.

I get a code for the EGR circut failure too.

It idles like crap, but runs great under acceleration.
Changed plugs, not wires and cap/rotor. Anybody want to give me an idea on what I should do?

Spin

 

[techieman33]

Did they use the explorers computer? Or switch it over the the mustang computer? If it's running the explorer computer than it probably needs to be tuned for the cobra motor.

 

[CobraMountaineer]

I dunno, the door is off the computer compartment, so I am guessing that the computer was swapped too. They got it into the firewall harness, and from there it is the cobra motor, wireharness, and etc. I am guessing that the computer is the Cobra computer because it is giving me OBD1 codes.