Preheat oven to 350°F. Grease a 13x9-inch baking pan with non-stick spray or butter and set it aside.
Drain the syrup from the can of peaches in a bowl and set aside. Place the peaches on a cutting board, and blot the moisture with a paper towel. Chop the peaches in small pieces. Sprinkle and toss the peach pieces with the flour.
In a large bowl, blend with a hand mixer or whisk together the cake mix, oil, eggs, and the syrup from the peaches.
Fold the peach pieces into the batter.
Pour the batter into the prepared pan. Bake for 25-30 minutes or until a toothpick inserted in the middle comes out with a few moist crumbs.
Once the cake cools, poke holes with a fork over the entire surface.
In a microwave safe bowl whisk together peach preserves and 1 tablespoon water. Heat in the microwave for 10 seconds, stir, then heat another 10 seconds or until thinned and smooth. Evenly pour the peach syrup over the entire cake.