[Jeff Chambers]

The O2s should toggle about .42, with greater than .42 being rich, less than .42 lean. What you really need is a break-out box if you can manage to find and borrow one. That'll let you measure the voltage at the PCM harness. At any rate, I'd still have to question what makes you think the problem is in the O2s and not elsewhere. The car may be running rich because of other issues, like the MAF transfer function being off. I'd really recommend seeking a good shop that has the tools to see where the problem is. Ask if they have a datalogger (like SnEEC) for the EEC-IV and a wide band.

BTW: It is possible for an excessively rich condition to register as lean with the O2's and vice versa. Also be wary of exhaust leaks. The smallest of exhaust leaks can wreak havoc with the O2s and have you chasing your tail thinking there's an electrical problem.