Preheat your oven to 350°F (175°C) to ensure even baking.
Grease your bundt pan thoroughly with cooking spray or butter and dust it lightly with flour.
In a large mixing bowl, combine the Duncan Hines Yellow Cake Mix and the pistachio instant pudding mix. Whisk together until well blended.
Add the eggs, water, vegetable oil, and chocolate syrup to the dry ingredients. Mix on medium speed until the batter is smooth, about 2-3 minutes.
Carefully pour the batter into the prepared bundt pan, smoothing the top with a spatula.
Place the bundt pan in the oven and bake for 30-35 minutes, or until a toothpick comes out clean.
Once baked, let the cake cool in the pan for 10-15 minutes, then invert onto a cooling rack.
Dust with powdered sugar or drizzle with chocolate syrup before serving.