Hey folks I'm still relatively new to the Boxster. Had mine for only 18 mos but have read a lot of exhaust threads trying to understand options and potential for drone.
I also had a Fiat X1/9 (don't laugh -- they're fun) that droned horribly after I put a performance header and exhaust on it. I used inserts like the ones shown here and they reduced the drone but never eliminated it. Most of insert companies recommend stuffing them with steel wool or adding more baffles to further calm the drone -- but then you're also reducing the performance of your exhaust. A good company with a lot of experience developing baffles is here:
https://www.carchemistry.com/
Several forum members indicate that the stock muffler and larger/heavier aftermarket mufflers don't drone because of their mass.
Seems clear that long-tube headers, removal of cat restrictions, and a lighter muffler will cause drone every time in our Boxsters.
The question is, can you change some of these items (header, and/or midpipe, and/or muffler) to improve performance or reduce weight without adding drone -- or incurring minimal drone.