Originally Posted by HP Autowerks
Check the clearance between the cross-over section of the exhaust and the chassis brace. Most shops will secure the exhaust as is sits may cause the cross-over pipe to come in slight contact with the chassis brace. Pre-load the system with a spin jack, then secure all the clamps, that usually does the trick.
How many miles did you put on the exhaust? There is a break-in period for the Borla system.
OP check what Harold said, I had this same issue and once fixed the drone is bearable and the trim pieces in the car stopped rattling. and I drive an auto