basically the idea is to take the temp average from the hottest cylinders being the rear most cylinders...if your temps are getting high then you know to get off the throttle, if you took it from the front 3 then you could see 1400 and already be too hot on the back cylinders, kinda like an idea of a be safe and not sorry i guess you could say..

measure the hottest cylinders because you would want to worry about the hottest to save the hotter cylinders

 

The more expensive 3-piece aftermaket manifolds come with the hole already drilled and tapped. OTR truckers are living in a little different world than diesel pickup truckers with way more fuel than they need, and in many cases way more fuel than their rigs are built to properly support.

Better safe than sorry.