So, they replaced the O2 sensor? Do you know what brand they used? Bosch seems to be the easiest to find, and if that is what they put in, it probably won't last long.

AC/Delco, Autolite, and Belden wires from NAPA are all good choices for wires.

I asked before he started and he said delco.

Went and got the plugs and wire, also a new air filter. Got lucky, they only had 7 55'* left in stock.

Already noticed better mileage so far. but ran the tank to fumes just to run a full tank test. It took 16 1/2 gallons for full, seems I didn't get as low as I wanted but still pretty much empty.