Combine all of the marinade ingredients, place tenderloins in a large zip-top bag, pour over marinade and marinate 6 - 24 hours. Refrigerate and turn occasionally. Combine all of the sauce ingredients, chill covered in the refrigerator. Prepare grill. Pat the meat dry, sprinkle with salt and generously with pepper. Brush the grill with vegetable oil. Place the tenderloins on the center of the grate. Cover and cook for 12 to 15 minutes, turning every 1 1/2 to 2 minutes, until the tenderloin reaches an internal temperature of 140 degrees F. To serve, slice the tenderloins, sprinkle with additional pepper (if desired) and serve with sour cream garlic sauce