Combine vinegar, salt, cayenne, red pepper flakes and molasses in a bowl, reserve half the sauce in a medium container and store in the refrigerator until cooking time. Add remaining sauce to ribs in a large glass bowl or glass pan, and marinate for at least 4 hours in refrigerator. Remove ribs and discard used marinade.
Prepare medium-hot fire and grill ribs over indirect heat. Close grill hood and grill turning only occasionally, for 1 1/2 to 2 hours, until pork is very tender. (Add extra charcoal if necessary to keep grill temperature at about 325-350 degrees F.) Baste ribs twice with reserved sauce mixture during last 30 minutes of grilling.
Serve remaining sauce with ribs.