1. In a medium bowl, combine 6 tablespoons of the olive oil, the 1/4 cup lime juice, 2 tablespoons of the cilantro, the garlic, and 1/2 teaspoon of the chili powder. Add the shrimp and set aside to marinate at room temperature for 10 minutes, turning them every few minutes.
2. In a small bowl, combine the sour cream, the remaining 1 tablespoon lime juice, the remaining 1 tablespoon cilantro, 1/4 teaspoon of the remaining chili powder, and 1/4 teaspoon of the salt. Stir well and set aside.
3. Heat the remaining 2 tablespoons olive oil in a 12-inch sauté pan over medium-high heat. Remove the shrimp from the marinade and season with the remaining 1/2 teaspoon salt and 1 1/4 teaspoon chili powder. In two batches, cook the shrimp for 2 minutes per side. Remove from the pan and allow to cool slightly before assembling the sandwiches.
4. Lay the tortillas on a clean work surface. Arrange one-fourth of the shrimp across the lower third of each tortilla, leaving about 2 inches of space on either side. Divide the lettuce, tomato, avocado slices, and grated cheese evenly among the tortillas, scattering them over the shrimp. Then drizzle some of the dressing over each. Fold both sides of each tortilla in toward the center, then roll the lower edge of the tortilla up, burrito-style, forming a wrap. Position the wraps on a serving plate, seam side down, and slice each in half on the diagonal. Serve immediately, or refrigerate and serve within 1 hour.
Yield: 4 servings