Use pure pumpkin purée rather than pumpkin pie filling.
Dark brown sugar may be substituted in the streusel when a more pronounced molasses flavor is preferred.
Whole milk gives the muffins a richer texture.
Sifting the powdered sugar before making the glaze helps produce a smoother, lump-free finish.
Do not overmix the muffin batter; stop stirring once the dry flour streaks have disappeared.