As I started reading this, I immediately thought Molasses. Bingo.
You can also substitute plain tomato sauce instead of catsup, use less so it doesn't taste too tomato-ey.
I looked at what I thought were my less sweet Bbq sauce recipes. My-my, they are full of sugars.
Here's one I found on About dot com/ Bbq sauces, not too sweet. Esp if you make suggested subs. I would add more hot pepper to this, but that's me.
Piedmont includes western North Carolina/ Kentucky, one of several US regions famous for its Bbq.
Piedmont Barbecue Sauce Recipe