this might sound stupid, but are boxster exhaust systems rigidly mounted

[thstone]

Originally Posted by particlewave

The exhaust is mounted to the the engine and transmission, not the chassis or body. The engine/trans/exhaust all move together.

^^^ What he said. ^^^

The entire system (engine/trans/exhaust) is mounted to the chassis at only three points: front engine mount (rubber isolation) and two rear transmission mounts (high viscosity fluid) to reduce NVH. Thus, the drone isn't likely coming thru the mounts, its just acoustic sound that is transmitted through the whole car. Do a search on exhaust drone and you'll find lots of posts about what others have done to reduce or eliminate it.