I installed mine because I (naively) wanted to reduce the temps in the back of the engine bay and try to preserve the all the wiring. I didn't see any change in the doghouse temps after putting them in. I ran a thermocouple probe to the back of the engine bay, above the driver's side valve cover just to see before and after. the only thing which affected the temps that far aft, was if i was driving or not and my temp delta between that and the intake was reliably 10 degrees (oregon in the winter). that's not to say they don't bleed off heat, i'm sure they do. just seems to be best for cooling the bay forward of the belts and such.
at least they look cool....
oh, and if you're concerned about EOT and ECT, the Bulletproof Diesel oil cooler has my endorsement. Was my first major mod and maybe it's overkill and a bit expensive, but making coolant and oil independent of each other is worth it.