Hi Rusty;
        Considering that my O2 sensor exhibits similar behavior as yours and I also measure downstream EGT temps (after turbo) right beside the O2 sensor and only see temps in the 700F range, I can't help but think that maybe the low temps are possibly the cause of the problem.

        I realize that you no longer have the turbo but you are measuring twice as far downstream as I. It doesn't seem likely the EGT could cool off enough in this distance, but why don't you clamp one of your spare T/C inputs to this location and find out for us?

S. Todd Bartrim
Turbo 13B
RX-9endurance
C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm

        "Imagination is more important than knowledge"
                                        -Albert Einstein