Attach sous vide wand to stock pot. Fill pot with water according to manufacturer’s instructions.
Preheat sous vide wand to 141°F.
Combine marinade ingredients in small bowl. Place steak and marinade in food-safe plastic bag; turn to coat. Seal bag, removing as much air as possible, and marinate in refrigerator for 1 hour.
Meanwhile, add peppers, onions, garlic, olive oil, salt and pepper to a food-safe plastic bag; toss to coat. Seal bag, removing as much air as possible.
Remove steak from refrigerator and submerge both bags in water. Set timer for 90 minutes.
At end of cooking time, carefully remove bags from pot.
Preheat grill pan or grill, and cook steak 2 to 3 minutes on each side or until internal temperature reaches 145°F. Carve steak diagonally across the grain into thin slices. Place steak slices on tortillas; top with vegetables. Season with salt and pepper, as desired. Serve with guacamole, if desired.
Nutrition information per serving: 317 Calories; 107.1 kcal Calories from fat; 11.9 g Total Fat; 3.7 g Saturated Fat; 0.2 g Trans Fat; 1 g Polyunsaturated Fat; 5.7 g Monounsaturated Fat; 73 mg Cholesterol; 348 mg Sodium; 24 g Total Carbohydrate; 4 g Dietary Fiber; 28.4 g Protein; 0 mg Calcium; 2.6 mg Iron; 623 mg Potassium; 0.2 mg Riboflavin; 8 mg Niacin; 0.9 mg Vitamin B6; 1.5 mcg Vitamin B12; 314 mg Phosphorus; 5.1 mg Zinc; 27.7 mcg Selenium; 105.5 mg Choline;