same problem
 

holy crap. i thought i was reading my own post. 02 non s boxster having same exact issue. about to buy a muffler, but now that i see your post, wondering if i need to buy mount instead. how did you do?

Did you guys figure out the rattle? Exhaust leak, heat shield, motor mount?
Just got my 2000 boxster and have same annoying rattle at low Rpms in gear. Thx!

As far as my knowledge goes, boxster’s cats are well known for failing. The result is quite funny... the cell unit in the cat frees itself and bounce & roll in the housing and eventually break apart. That create the same rattling sound as described in this thread.

I am getting a buzzing sound when coming off the throttle. It is like a heat shield vibrating. I have no secondary cats. Seems like it could be a shield in the engine compartment as the sound is very loud with my engine cover/mat off.

What is it it???