Warm meat to room temperature. In a small bowl, combine soy sauce, sesame oil, garlic, ginger, and MSG. Place tenderloins in glass or enameled pan, pour marinade over meat, cover with plastic warp and let sit overnight in the refrigerator.
Place meat on a charcoal grill (with moistened hickory chips added to smoke) over indirect low fire. Barbecue with lid closed, turning every 15 minutes and basting with marinade, about 1 1/2 hours.
Mix together BBQ sauce, soy sauce, sesame oil, and garlic. Heat.