Heat a dry skillet over medium heat, and toast the peeled garlic until cloves are browned on all sides. Remove from skillet and transfer to small bowl to cool. Add cumin to the skillet and toast over medium-low heat until fragrant, about two minutes.
Use a food processor to combine the cumin, peeled cooled garlic, Aji Panca Chile Powder and vinegar. Pulse mixture until ingredients are well combined. While the food processor is still running, slowly add olive oil to the spices and pulse, until thick chile-garlic paste forms. Season the paste with salt and pepper.
Cut sirloin into strips about 3 inches long, 1-1/2 inches wide and 1/4 inch thick. Thread the pieces individually onto a skewer. Arrange the beef skewers in a lightly-oiled baking dish, spreading the chile-garlic marinade over the top of the meat with a spoon, coating both sides of the beef strips. Cover dish with foil or plastic wrap, and chill in the refrigerator for 2 to 4 hours.
Prepare a hot grill outdoors, or preheat a dry grill pan over high heat. Drain marinade from the meat, throwing out the excess marinade. Arange skewers on the preheated grill or indoor grill pan, and cook kebabs until sirloin strips are sizzling and cooked through, about 3 to 4 minutes per side. Serve immediately.