Maybe the agave. Lots of fructose there. Frankly, I'd skip the sweeteners - you can glaze after they come out of the foil or, not my preference but many like it, sauce after foiling. Try one or more juice reductions or one or more of these with the addition of a little reduced stock. (A favorite of mine: somewhat reduced pineapple juice mixed with wither pom molasses or tamarind concentrate.) Just a couple or 3 T for backs, 4-6 for sides, meat down.
Me, I remove from foil when tender in the foil - then return to the cooker unfoiled to restore bark texture. Doesn't take long. (If glazing - I never sauce - I do so after a few minutes unfoiled, just one or two very thin applications with a pastry brush, a very thin veneer, so the bark texture and color comes through.)