I struggled for a long time with overheating on my 2G whenever I tried to run the AC. I tried a lot of the basics that Halon did on his 1G above, but nothing worked.
In the end, I installed one of the flex-a-lite/fal (I'm sorry I don't remember the exact brand) twin-fan shroud kits and ALL my problems went away. Something like whats pictured here:
http://www.boostcontroller.com/index.php?item=494
Also something I have noticed, cooling system on the evo8/9/X is setup so much better than the DSM's, it's like magic... having the FMIC on there from the factory is such a blessing. Sometimes I forget how good I have it.