Pulled Pork with Root Beer Sauce

1 (2 1/2-3 lb.) Pork Sirloin roast
1/2 tsp. salt
1/2 tsp. pepper
1 Tbsp. cooking oil
2 medium onions, cut into wedges
1 2-liter Bottle Root Beer
6 cloves garlic, minced
3 c. root beer (2 12 oz. cans)
1 c. bottled chili sauce
8-10 hamburger buns

Trim fat from meat. If necessary, cut meat to fit into your slow cooker. Sprinkle meat with the salt and pepper. In a large skillet brown meat on all sides in hot oil. Drain off fat. Transfer meat to cooker. Add onion, the 2 liter of root beer, and the garlic. Cover and cook on low-heat for 10 hours or on high heat for 5 hours. Transfer meat to a cutting board or serving platter. In a sauce pan stir together the 3 c. root beer and the chili sauce. Bring to boiling; reduce heat. Simmer, uncovered, stirring occasionally, about 30 minutes or until mixture is reduced to 2 c. If desired, add hot pepper sauce. Put sauce aside. Using 2 forks, pull meat apart into shreds. Using a slotted spoon, transfer onion to serving platter; discard juice. If desired, line bun with lettuce leaves and tomato slices. Place shredded meat and onion on rolls. Drizzle meat with root beer sauce.