Setting up the Derale electric fan control yesterday and while I had the infrared gauge out I took some measurements of the header temp at each cylinder. Engine was warm up to 190, cylinders 1,2,7,8 were pretty close to each other in the mid 600's (F). 3,4 were a bit lower but nut much, high 500's to low 600's. 5 and 6 is where my readings went all cattywompus. 5 hit about 748 on the upper end and 6 was in the upper 400's. Sparkplug #6 looks good, seems to be firing so I don't think there's a miss there. So I'm trying to think this through and figure out my discrepancy. Only thing I can come up with is maybe a vacuum leak in the intake gasket @#5 causing a lean condition thus burning hotter. Anything else anyone can think of?