Forgot to mention I changed the o2 sensors 20000 miles ago.

I'm running the plugs and wires DiscoMike recommended at a Bay Area shop he recommended so believe they are good since they are only 20000 old also.

Perhaps it is tire pressures or my wife's heavy right foot?

Dammad.

 

After I read this I'm starting to think I may need new O2 sensors. That or the 33's bring the mileage down to about 10 mpg. I have almost 75k, think they could be the culprit? I also don't mash the pedal at all.

 

Yes bigger tires will bring your mileage down. Especially if you are still on the stock gears boxes and axels. How much I don't know. If you are not getting any codes for o2's I would not change them.

The Goose