Again, the number of ports really has no effect on the powerband (low/mid/high) of the engine it-self. The port timing does (location of the ports vertically in the sleeve ).
For example, the Speed is only a 4 Port motor, but has PLENTY of top end.
Alpha has 2 different 7 port engines, one tuned for top end (more duration) and one for low/mid (less duration).
So to say a certain pipe should be used on a engine with a certain number of ports is kind of vague.
Best place to start is to run the pipe that is recomended, or at least talk to people (who know what they are doing) about what to use on a particular engine.