2003 Boxster rear end noise

[eomak]

Hi all,thx for replies.I drove it around some more and noticed it at idle too and has that sound as if from the cats. If u rev. the car just slightly at idle even on a cold start some times u can hear a little rattle,buzz noise.The thing that gets me is that sometimes it doesnt even happen and sounds nice a smooth until it starts to rattle again. So as long i dont see any warning lights on the dash it could be something minor loose or cats and would it be porsche warrnty if cats?Has 50km's.I guess it wouldnt be from the tranny if i can hear it at idle no?
I'am taking it to my porsche mech. next week but hopping i could find the problem before then.Also would it be cheaper to take it to a local brake shop to have brakes done and i supply the parts from Pelcian parts and just pay for the labour?My porsche mech. is gonea charge me $850 Canadain just for the front brakes pads,rotors,labour not sure if they need new rotors though.And for a full replacement clucth if needed $3200, that sounds right?My 911SC is around $1300.Other then those worries the car drives great in town and on the highway.Oh and one more thing where do u get those Hardtop's and how much new or used?And it just sits on top the car with specail locks? The secondary cats u can take off and have staight pipes going threw with no warning lights and it well still pass emmsions no? Fabspeed pipes.