To Make The Chicken Tenderloins: In small bowl, combine paprika, onion, garlic, cayenne pepper, white pepper, crushed fennel seeds, thyme and salt. Sprinkle mixture evenly over tenderloins. Cover and refrigerate for 1 hour.
Preheat grill for direct heat cooking. Grill tenders 5-6 minutes until meat thermometer reaches 170 degrees and turkey is no longer pink in the center. Turn tenderloins over halfway through grilling time. Remove from grill and squeeze lime over chicken pieces; allow to stand 10 minutes. Slice into 1/4 inch strips.
Fill each pita half with chicken, lettuce, avocado salsa and the sour cream sauce.
To Make The Avocado Salsa: In small bowl, combine avocado and lime juice. Stir in tomatoes, green onion, green pepper and cilantro. Cover and refrigerate until ready to use.
To Make The Sour Cream Sauce: In small bowl, combine sour cream, onion, chilies, cayenne pepper, black pepper and salt. Cover and refrigerate until ready to use.