No there is no benefit whatsoever to the slight machine work done on the exhaust port exit. Firstly it is only the very exit that has had a circular taper on it to essentially diverge the D shaped port into a circular exit, the throat and seat area are std cvh in profile. This machining op was done to all CVH engines in that period that used a round exhaust manifold port, not just the RS1600i. It is however of no benefit to power whatsoever.