So while eating our gringo tacos today at Tito's, Mr. Creosote and I were picking through the salsa (and the dumpster, clearly we've hit a new low) to look for clues.
Upon closer inspection (see photos), we noticed tiny bits of carrot and that the chiles seemed an olivey green color intead of bright, and I'd mentioned a possible vinegar connection in your previous inquiry. Well, when you eat just the little bits of carrot, they tasted slightly vinegary and cooked...so I'm thinking there's pickled/marinated Mexican vegetables in it. Yeah? Oh, and judging from their garbage, they use a bunch of different kinds of tomatoes, including Romas. Hope this helps.