[Blue Streak 21]

I had this same problem with my car last year. Have you checked the fuseable links in the harness? I had one go bad in my system while I was chasing my electrical gremlins. To diagnose the problem I pulled the harness out of the car, unwrapped it up and found a couple of bad wires and a possible short down one of the O2 sensor wire branches.
The harness also had a bare wire near the big ECU connector. The wire was rubbed bare where the harness crosses the raised edge of the metal shelf that holds the ECU.