I removed all mufflers initially, then I added a magnapack (the round ones) to the middle, and now replaced that with a 24" magnaflow. No mufflers in the rear at all. With this setup there's not a lot of droning, but the sound has turned a little too tame for my liking (no more proper crackles, I'll post a video later). I purchased the Borla ProXS Mufflers 40364 which is smaller and likely will improve the sound but am waiting to get my tune from
@Livernois before I make any further changes as their tune should improve the sound somewhat too.
I ran into the same problem. Borla said they could build it for me, but would need my car for ~4 weeks in order to do so. I went to a local muffler shop instead, who built me a custom exhaust for half the price of the Borla cat back. The sound is fantastic.
What mufflers did you remove?
I removed all mufflers initially, then I added a magnapack (the round ones) to the middle, and now replaced that with a 24" magnaflow. No mufflers in the rear at all. With this setup there's not a lot of droning, but the sound has turned a little too tame for my liking (no more proper crackles). I purchased the Borla ProXS Mufflers 40364 which is smaller and likely will improve the sound but am waiting to get my tunes set up before I make any more changes since the tune should (theoretically) make it sound a little better.']Link here for sound + pics of the setup.