sweetener is eltyl maltol aka EM. its used to sweeten, but its also used in tiny amounts (<1~5%) to make flavors 'pop', come together, and give more of a fuller effect.
im just gettign into EM myself, so i only have base knowledge.
some other notable additives that give a worthwhile effect are lemon
juice, vinegar, and water. then theres the magic mask, and bitter wizerd, and possibly more that i cant seem to keep straight. i tried posting an 'additives' thread to sort them all out without much luck :/
perhaps we'll have better luck compiling such a list (with percentages) here.
if not, check out the daunting 'Vinegar?' thread. but be warned, its long. and have your notebook ready!