After much deliberation I have decided to get the following eaxhaust for the Boxster. Its a new design Mille Miglia and I am assured that there is NO resonance at all in the cabin. The gases flow from the sides into the middle to a mixer box. The gasses then return back into the muffler which has perferated pipes and muffler packed with fibreglass then exist via S style tips. Following is a pic. It produces a claimed 12kw increase in power but I am scpetical about this, just like the look and the richer tonier Porsche sound that it produces.
I will get some pics and recording when it's on.