Heat vegetable oil in a non-stick grill pan over medium high heat.
Cut chicken breasts into slices about a half inch wide; season with salt, pepper, and garlic powder.
Place chicken slices in pan (about 8-10 at a time) and grill until browned and juices run clear, about 3-4 minutes on each side. Repeat until all chicken is cooked.
Meanwhile, process chipotles in adobo in food processor until fine. Add in the BBQ sauce and process to make sure everything is pureed.
Remove chipotle BBQ sauce and place in small saucepan over medium low heat until warmed through. Drop a few chicken pieces at a time in the sauce to coat.
Place tortillas between 2 damp paper towels and microwave 30 seconds.
Build your wrap: layer a few chicken pieces, lettuce, and cheese in middle of tortilla. Add sour cream if desired. Leave about 1-2 inches of tortilla at bottom with no fillings. Fold one edge of tortilla over, then fold up the bottom, and finish by folding over the remaining edge.