Spyder,
Your problem could be from a number of sources. Many flavorings have sugar added, and the by-products of the combustion of the syrup might disagree with your body chemistry. Also, aromatics tend to be more moist than non-aromatics, so the additional water could contribute, as steam is more likely to burn your tongue than hot smoke, so try drying out your tobacco by leaving it out on a piece of paper for a couple of hours before loading a bowl. Finally, most aromatics are primarily Burley because that leaf absorbs flavorings better than any other strain. Your problem might be that Burley doesn't agree with you.
Russ Ouellette