Prepare Chimichurri Topping. Set aside. In a large bowl, combine beef, pork, chili powder, onion powder, cumin, and salt. Mix well. Shape into six 1/2-inch-thick patties.
For a charcoal grill, grill patties on the rack of an uncovered grill for 10 to 13 minutes or until an instant-read thermometer inserted into side of each patty registers 160 degrees F, turning once halfway through grilling. (For a gas grill, preheat grill. Reduce heat to medium. Place patties on grill rack over heat. Cover and grill as above.)
Place each grilled patty on top of two of the pita quarters. Top with roasted peppers and Chimichurri Topping.
In a small bowl, combine finely snipped fresh flat-leaf parsley; finely snipped fresh cilantro; red wine vinegar; olive oil; garlic, minced; salt; ground black pepper; and cayenne pepper.