Saute the minced garlic in 2 tablespoons of olive oil on medium low heat for 3-5 minutes be careful not to burn. Remove from heat an let cool for 10 minutes
Rinse shrimp; pat dry. In a resealable plastic bag combine remaining olive oil, garlic, chili powder, and 1/4 tsp. salt; add shrimp. Seal bag and turn to coat shrimp; chill 30 minutes.
Meanwhile finely shred peel from lime; juice lime. For lime slaw, in a large bowl combine the lime peel, lime juice, cabbage, and remaining 1/4 tsp. salt; set aside. In a small bowl combine sour cream and chipotle pepper; set aside.Wrap tortillas in foil.
Thread shrimp on 10-inch metal skewers. Note(If using wooden skewers, soak in water 30 minutes before using.)On a covered grill, grill tortilla packet directly over medium heat for 5 minutes; turning once. Add shrimp to grill; cook 5 to 8 minutes or until opaque, turning halfway through grilling. Remove tortilla packet from grill. Remove shrimp from skewers.
Shrimp can also be cooked on the stove-top in a skillet and tortillas can be heated in a 350 degree oven.
To serve, spread tortillas with sour cream mixture. Top with lime slaw and shrimp. Sprinkle with cilantro and avocado slices, if desired.