For the bread:
Preheat oven to 350° degrees.
Grease 9-by-5-inch metal loaf pan; dust with flour.
In medium bowl, stir together flour, baking powder, baking soda and salt.
In a large bowl, with mixer at low speed, beat butter until smooth.
Add sugar and beat until creamy.
Beat in vanilla.
Reduce speed to low and add eggs, one at a time, beating after each addition until well blended, scraping bowl occasionally with rubber spatula.
Add flour mixture alternately with sour cream, beginning and ending with flour mixture.
Fold in blueberries.

For the streusel:
With fingertips, mix ingredients until blended.
Spoon batter into prepared loaf pan.
Sprinkle streusel over batter.
Bake 1 hour and 15 minutes to 1 hour and 25 minutes.
For mini loaves, bake about 40 minutes, or until the bread tests done with a toothpick.