Personally, I like the New Zion Missionary Baptist Church and BBQ in Huntsville. It's a quick shot and easy to find off of the interstate. The 'cue is pretty darn good and the pies are great. I always get a pie to take home.
That's a really out of the way detour, almost 3 hours.
I've never found anything earth-shatteringly good between Conroe and Dallas. If I were near Dallas again I would head to Fred's in Fort Worth. That is one awesome place!!! http://www.fredstexascafe.com/