1999 Disco, 180K miles

I've flushed the coolant and radiator, replaced upper/lower radiator hoses and installed 180 degree thermo. Of course I can't trust the idiot gauge to tell me the correct temp, so I'm going to order a diagnostic tool. In the meantime, I'm taking the train to work. No big deal.

Anyway, for sh*ts and giggles I measured the temps just next to each spark plug with an IR reader and I noticed that the number 8 cylinder is always much higher (100 degrees) higher than the other cylinders. This worries me.

I've tried to research here and on the web, but couldn't find anything.

Question: Is this normal or acceptable?