Preheat the oven to 375 degrees. Line a standard 12-cup muffin tin or a jumbo 6-cup muffin tin with paper liners.
In a bowl, combine flour, baking powder, baking soda and salt; set aside.
In the bowl of a stand mixer fit with a paddle attachment, beat sugar, vegetable oil, eggs and yolk, and vanilla extract on medium until combined, about 30 seconds. Add water and beat until smooth. In three additions, add flour mixture, alternating with sour cream, until combined. Scrape down the sides of the bowl and add 2 cups of chocolate chips. Beat until just incorporated. Divide batter evenly between prepared muffin tin, filling paper liners all the way up. Sprinkle them with remaining chocolate chips.
Bake in the center of the oven until muffins have risen above the pan, and a toothpick inserted into the center comes out clean, about 25 minutes for standard muffins, and 35 for jumbo.
Transfer to a wire rack to cool slightly. Enjoy warm or at room temperature.