For me, it's a taco shell. I can have a taco salad and all that jazz, but honestly, it's the one product other than ketchup that I just won't substitute. As with ketchup, which I hardly ever eat, a good old fashioned taco shell just can't be beat. I never have more than one, and calculate the carbs accordingly. I'm curious - what high carb item are you willing to negotiate around?