Wideband UEGO Air/Fuel Sensor

If you have limited funds, they might be better spent at the drag strip or on a dyno since those actually measure performance.

Sorry I disagree. Wideband has helped me in numerous ways, and 'around here' a dyno (and a track as well) is rare and expensive. By the time I drove or trailered to Spokane round trip and spent money on a dyno run, all that more than paid for the cost of a wideband. I realize they have limitations and are not "lab quality" so to say

In my opinion the current crop of affordable O2 meters are one of the best things to help guys who are "alone" in the hobby with limited test equipment

Another great tool is my old G-tech or some other onboard performance device. G meter is very helpful