I've put about 300 miles on the wagon now since the tune. Aside from a strange high idle issue, it's running really well and seems really happy. Changed the oil yesterday, but forgot to save some to send to Blackstone. So far, it looks like I'm averaging 200 miles per tank and 14 miles per gallon.
On an unrelated note, my Bimmerforums Secret Santa sent me an excellent gift. If you're still stalking me, thanks again, Secret Santa. :) Need to fab a bracket and stop at Radio Shack, then I will install.