Did you already flush your coolant? If so, you may want to keep a keen eye on your temps, as most folks who have flushed without rebuilding the oil cooler have been back under the hood very quickly for that job. If you haven't flushed yet, I would advise waiting and allowing the delta to spread to 15* before making the switch and rebuilding/replacing both coolers. Take that time and learn everything you can, and decide which EGR cooler solution is right for you.
Yes, thanks to your sticky on bulletproofing, one of the first things I did was to replace the coolant with ELC (Zerex from NAPA, in my case). I also installed an Edge Insight and have been watching ECT/EOT and noticed the deltas are looking good right now (9* is avg). Next step there is to also get the EGT sensor installed so I can keep an eye there, too.
I've also been putting my foot into it about 3 times a week during my drive home, and then allowing everything to cool down before shutting the truck down. The excessive idling has me a little concerned but mainly from a $diesel$ perspective. So far this truck has been great!
If I can get the code revision that's put on there today, I'll post it here, along with MPG findings. I have a feeling that I might not see significant MPG improvements until I take the EGR out of the picture and maybe get a tuner.
**P.S. - Nice Porpoises by the way - my first CTT instructor at Corry Station was on subs for over six years before he and I crossed paths...a long, long time ago.