Here's an easy way to both fix your problem and get more accurate readings.
1) buy a new, single wire 02 sensor, preferably a wideband one.
2) take your car to the local exhaust shop, ask them to drill your downpipe, just before or after the before-cat o2 sensor, and weld on a bung for the new o2 sensor. have them then thread a bolt, or your new sensor, into the bung.
3) take the car back to your garage and hook the sensor wire of your gauge up to the wire on the new O2 sensor. If they put a bolt in the new fitting for the ride home, remove the bolt, apply some anit-sieze to the threads on the sensor, and install the sensor into the exhaust pipe.
Now, you have a highly accurate a/f gauge setup that does not interfere with the factory emissions control system, it acts on it's own circuit (the gauge itself).
You could always put a switch on the signal wire, so you can disable the gauge when you don't want it messing with your ECU. just turn the switch on or off before starting the car
You usually only use the gauge when tuning anyways...