In a small bowl mix together the garlic powder, onion powder, paprika, salt, and cayenne pepper.
Add the potatoes to a medium bowl. Sprinkle on the seasoning and toss together.
Heat a large skillet over medium-high heat and add the diced potatoes. Cook for 10-12 minutes or until they are crispy on the outside and soft on the inside.
While the potatoes are cooking get the chipotle sauce ready. Add the fat-free sour cream, chipotle peppers in adobo, lime juice, and taco seasoning to a food processor or blender. Run until the sauce is well combined.
To assemble the tacos, add 1/4 of the potatoes to each shell. Top with lettuce, cheese, and chipotle sauce.