Here are some that I have done, either on a kettle or UDS, always over a mixture of lump, briquettes and applewood, sometimes pecan or peach too.
All of these have sugar in the rub, usually turbinado and I am pretty sure the heat is always around 270F to 280F as that is where I run my cookers normally. There is a range of colors, and some of it appears burned. There is no carbon taste at all to any of these. I believe it is not the sugar, if you are getting burned flavors, look to the fire and how clean it is burning.