Cut the pork into approx. 1 inch chunks. Prepare marinade by combining garlic, soy sauce, sesame oil, lemon juice, mustard and red pepper flakes in a bowl and mix well. Add pork chunks and stir to thoroughly cover the meat. Refrigerate and allow to marinate for 2 hours (longer if desired) Remove pork from marinade and thread on skewers, leaving space between each chunk of meat. (NOTE: I use the flat metal kebab skewers, if you use wood skewers be certain to soak in water while meat is in marinade). Place skewers on a rack over a cookie sheet lined with foil. Sprinkle with black pepper and garlic powder to taste and place under broiler, approx. 3" from heat for 5 minutes. Turn kebabs and broil for another 2-3 minutes. NOTE: You may brush with marinade during turning, if so desired.