Preheat your grill over medium heat. Brush the grill grates with olive oil.
In a large bowl, whisk together the olive oil, chili powder, ground cumin, garlic powder, onion powder, salt, black pepper, and cayenne pepper. Add the shrimp to the bowl, and toss to coat. Set aside to marinate for just a couple of minutes while you prepare the salsa.
In a large bowl, toss together the tomatoes, onion, jalapeño, mango, cilantro and lime juice. Set aside.
Once your grill is hot, place the shrimp directly on the grill grates. Alternatively, if you have skewers available, you can skewer the shrimp to hold them in place. Cook for about 3-4 minutes on each side or until pink and fully cooked through. Remove from heat and transfer the shrimp to a cutting board. Give them a light chop and add them to the bowl with the salsa. Toss to combine. place the diced avocado on top. At this point, you may gently fold in the avocado if you wish, but be careful not to mash it too much. Sprinkle with remaining cilantro.