After much money and time, the '92 Deville 4.9 now runs amazingly. Turns out, we DID get a bad ECM from the after market place. Bought one from GM and all is well. In fact, we are gonna stick with GM parts, I think. Cadillacs are particular.
Anyway, we had a minor fuel line leak and are replacing the tank, because of the problem with the broken baffles. We'd been putting it off, but since we had a leak, just figured we'd go ahead and fix it. You can see the broken plastic bits there. The new tank has no plastic.
The ABS light has been coming on, we think that perhaps the leaking fuel line (by the left rear tire) may have been causing fuel to make the sensor mess up. Only time will tell if that theory is correct, since the new tank replacement is going slowly due to time constraints.
Otherwise, this car remains a joy to drive. The body and interior are still in amazing condition. Nothing beats a nice big comfy Caddy.