why is it that the rear cylinders on most engines, the ctd's
especially, run hotter then the rest? is it simply a function of them being tucked away further in the back, or is there a operational reason?

 

Tucked away in the back is one, but another is if you look at the intake thats cast into the head it really necks down toward the rear which kills the air flow under high boost/volume demands and will raise EGT's. Plus the coolant goes from front to back so its warmer when it gets to the back cylinders.