Streusel topping: Combine brown sugar, flour, butter, and pecans
Mix together until crumbly
In a separate bowl combine cake mix, cream cheese, eggs, water and oil and mix by hand or with a hand mixer just until mixed
Oil/grease/spray a 9 x 13 inch pan
Put HALF the batter in the bottom of the pan. Spread it out - it will be a little thick
Sprinkle blueberries on top of batter
Top with remaining batter
Sprinkle streusel evenly on top of the batter
Bake in 375 oven for 45 minutes OR until the cake temperature is 170+
Remove from oven. Let cool. When cool, cover and keep at room temperature for 24 hours.