similar to what BMW used on their first generation of helmets, universally known as golf ball helmets, they claimed it reduced turbulence. the idea came from golf balls which travel much further and straighter with the dimples they have. a golf ball with no dimples is demonstrably weaker in accuracy and distance
maybe in an intake port it promotes speeding up ( or less resistance ) of the charge. i think the principle was that air will hit the far edge of the dimple, circle round and when it comes out takes any passing charge with it. could be wrong but my failing memory tells me something like that
