In a large bowl whisk together the balsamic vinegar, garlic, chili flakes and canola oil-add pork chunks, toss well, and if you have a freezer bag pour into that-remove as much of the air as you like and place in the fridge overnight-turnning a few times.
At this point you can also freeze for later use.
If using wooden skewers pre-soak 1 hour before using, and you will need 14.
In a large bowl whisk together the ketchup, vinegar, brown sugar, soy, ginger, salt and sesame oil.
Preheat your grill to medium high.
Skewer the pork, pineapple, tomatoes and peppers, repeat until all skewers are done.
brush skewers with the ketchup/soy sauce and place kebabs on grill, basting often and turning twice.