How do you know that youre running rich? Stock o2 sensors (narrowband) oscillate between .1V-1V. But youre not going to be able to read that with a multimeter, its just too fast for the meter to pick up. You need an oscillascope. .450V =stoich. There is no way to test o2 sensors out of the vehicle. Heater circuit should be around 20 Ohms, but that will not pass nor condemn an o2 sensor. Just my .o2

 

cause my vac hoses are where they should be and black smokes is telling otherwise