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.
I'll go back to the muffler shop and have them check that out again tomorrow night. I bought the exhaust used and it shows sign of wear so I assume the Borla should be past break-in already.
I had a friend ride along with me who examined the rear cabin while I accelerated in the troublesome 1500-2000rpm range and confirmed the vibration wasn't coming from a loose trin piece (before with the stock exhaust the vibration definitely wasn't there.).