For what it's worth, Motec (Fuel Injection Company) tech guys will ALWAYS recommend monitoring air fuel ratio over EGT. From what they say, O2 (lambda) sensors are more accurate, more reliable, faster acting and tell a more complete story. In the context of my supercharged motor, they mentioned that if a tune-up was a fair way off base, the EGT could read warm, hot, hotter, REALLY hot, then cooler -- all while the air fuel ratio is leaning out more and more. In this case, the EGT would be giving "false" readings, ones that a corresponding change in tune-up that will make head gaskets most unhappy....
