As I understand it the theory of "rough/port polish" is to keep or create turbulence to atomize and move the the fuel load more efficiently. A too smooth entry can create static air cavitation on the port wall.Whether this theory holds true for 6 cylinder inlines I can't say. As to the exhaust ports, I've read that 6 cylinder inlines are notoriously poor in dumping exhausted fuel at the port opening and benefit from some smoothing and gasket matching.
