Ok
I only mention the meter b/c there is an easy way to test the 02 sensor on HFM/SFI units

The connector is under the rug , passenger side
If the meter is hooked up to sensor output sig wire, one simply takes the vac hose off the fuel pressure regulator and watch for the meter to go rich
[ high voltage - .9v]. You put that vac hose back on and then you can test for lean reading [ low volts - .1-.2v] by simply creating a vac leak by removing a vac hose . [The one going to SOVs is fine]
All is this does is you are manually making the engine run rich/lean and seeing if the 02 sensor responds to your inputs by watching for the voltage output of the sensor to change accordingly.
It is easy to change these engine mixture inputs manually b/c the car is EFI.
If the 02 responds , you know you do not need a sesnsor.
just a quick DIYer trick.
I don't like changing any parts til I see they are not working....
Your sensor may also just be carboned up from previous rich running and just needs a high speed run down the Pike for a few in 3rd...