Mexican Fiesta is a blend of spices that we regularly buy from Whole Foods. Here is the ingredient list:

Chili peppers, onion powder, tomato powder, paprika, cumin, garlic, cilantro, oregano, cayenne, lemon peel.

I'd suggest first adding spices that will add flavor and 'dial down' the Nerve Toxin factor...and then gradually adding more chili pepper/cayenne/chili powder type spices to get it up to the hotness that you like. (Personally, I don't care much for cilantro and would replace it with regular parsley if making my own "Fiesta".) Hope that helps!