Spark plug readings may fool you into thinking you're lean when you really aren't. With an MSD or other high-energy ignition it takes much longer to develope any color to the plugs. I can run on the track for a whole weekend and the plugs come out bone-white when I'm jetted 1/2 a jet rich. To properly read a plug you have to cut the threaded part off exposing the entire porcelain and "read" the very base of the porcelain.
