Just a final update. The Japanese crew was able to isolate the exact part of the circuit that was throwing the error. The mechanics said it was easy to locate within the engine and once they found this circuit sure enough a small "sliver" of metal was present. This was removed and the car was driven by the mechanics and they felt this fixed the issue.
I have personally driven it a couple of times and it is running beautifully. I definitely think it was modulating something once the check engine or knock sensor was triggered, because it wasn't accelerating normally as I had remembered. Now that they've fixed it it appears to be running well, just as it was from our test drives.
Thanks again for everyone's input.
