Heat olive oil in a pan over medium heat. Stir in onion, jalapeno, garlic powder, cumin and 1/2 teaspoon chili powder. Stir in pork and cook just until warmed through. Stir in cilantro. Remove from heat.
In a small bowl combine mayonnaise, lime and remaining chili powder.
To make one sandwich: spread mayonnaise on toasted bread, top with 1/4 of the pork mixture and 2 slices of avocado. Serve.