The easiest way i can think of is to install a a/f ratio guage. Though I found that on the MAX it is not an exact science. My 95 se has three(3) o2 sensors and I found that the one nearest the engine( left cylinder bank right at the exhaust manifold) gives the more acurate reading. Though the a/f guage is nothing more than a fancy voltmeter I think you wouldhave a hard time converting a meter reading to a ratio.