the recipe that everyone was talking about? I found it mentioned in another thread.
This looks very much like a concoction I've been using for a few years. The seasonings look nearly identical to what I use, but I think that's entirely too much citrus juice to use in a marinade, and entirely too long to let the chicken marinate in that much citrus. I can only imagine the toughness of the meat and the flavor of lime invading every corner of your mouth. Almost like a lime-chicken flavored sour candy....
I've also never grilled my tequila-lime chicken, but I very much doubt that is the cause of your troubles.
Here's the problem: you really want that lime-tequila flavor in your chicken, and you'd almost have to use as much citrus juice as that marinade calls for to permeate the chicken, but the acid also "cooks" it while delivering too strong a flavor.
I always cook the chicken using a little bit of tequila, 1/2 a cup sounds right for the amount of chicken in the recipe. When it is nearly finished cooking I like to spike it with a little bit of lime, not drown it. I also always use my tequila-lime chicken almost exclsively for chicken tacos, so here is where I differ. I use equal parts of thinly sliced red onions, red/yellow bell peppers, and then some roughly chopped cilantro as a vegetable topping for my tacos. I toss these veggies in a little bit of lime juice, b/c they'll hold onto the flavor a little easier than the chicken will. This way, you have the tequila flavor in your chicken to match the slightly "limey" flavor of your veggies, and they really combine well this way, IMO.
If you would rather serve the whole chicken breast as described in the recipe then I would suggest mixing together the same combination of veggies listed above, and cook them to use as a side, maybe with some rice, for your chicken. If you dont like that idea either, then I would suggest tweaking that marinade. When I look at it the amount of acid in it really sticks out to me as the most likely problem. Tequila-lime chicken really is a very tasty dish.