[Dave Noll]

YES, a mis-fire will show lean on a wideband sensor. All that sensor reads is oxygen, when there's a mis-fire, oxygen isn't getting used on that cycle so it passes through the engine un-used. A wideband sensor in a collector is seeing the average of 4 cylinders. If say theres a distribution problem in an intake manifold, the average of the 4 could show close to perfect, but with the bad intake it may have a severely lean hole. The better way to check would be to weld 8 bungs into the primary tubes of the headers and either install 8 sensors or rotate 1 sensor over 8 passes down the track.