Cook corn syrup and sugar together in a large saucepan or Dutch oven over medium heat, stirring to dissolve sugar. Bring mixture to a boil (OR in a 2-quart microwave safe bowl, microwave on HIGH (100%) for 2-1/2 to 3 minutes. Remove from heat. Stir in peanut butter until blended.
Add cereal, pretzels and chocolate pieces; stir until coated. Press into a greased 15 x 10-inch pan. Cool and cut into bars or triangles.