[90supra]

I average about 200 miles to the tank no matter how soft or hard I drive her. Its a 6cyc, automatic with a K&N ram air, new spark plugs, new oil, new brakes, new tranny fluid, and maybe some other stuff. I checked to o2 sensor and I believe it is in working order but not sure. Which wire do I check the voltage on the plug? What else could be the problems, no check engine light even with o2 unpluged.... Help please, my Supra got at least 20 mpg running it hard.