Whisk together pudding mix, sour cream and milk in medium bowl; set aside.
Place 1-1/3 cups peanut butter chips and oil in small microwave-safe bowl. Microwave on HIGH (100%) 45 seconds; stir and microwave an additional 15 seconds; stir until smooth. Using a hand mixer on high speed, gradually add to pudding mixture; spread evenly into crust. Spread chocolate fudge topping over pie; cover and refrigerate 6 to 8 hours.
Prior to serving, top with remaining peanut butter chips.