In a mixing bowl, combine olive oil, lime juice, chili powder, cumin, garlic powder, salt, and black pepper. Add the sliced chicken and toss to coat. Marinate for at least 15 minutes.

Heat a skillet over medium-high heat. Add the marinated chicken and cook for about 5-7 minutes until browned and cooked through. Remove from skillet and set aside.

In the same skillet, add the sliced bell pepper and onion. Cook for about 5 minutes until softened. Return the chicken to the skillet and stir to combine.

Warm the tortillas in a dry skillet or microwave. Serve the chicken and vegetable mixture in the tortillas with sour cream, shredded cheese, and guacamole.