Most everyone installs the Tru-Cool Tranny Cooler. I did it and like mentioned run 150ish. Last week I pulled an empty 24 ft Haulmark Trailer about 3500 LBS and ran about 190.
There is tons of info on this forum about it.
IMO this is 1 of the best MODs for the money you can do.
Here's the link to the search for "Tru-Cool"
http://www.elcovaforums.com/forums/s...earchid=264624