American Racing Headers on 2011 GT500 with stock exhaust?

So I've done numerous searches on the topic with no success to my specific question. The question is about loudness and drone with American Racing headers and the stock exhaust for a 2011 GT500.

I currently have Corsa performance exhaust specific to the GT500, and you can hear the sound on youtube, and there is also a video with the AR headers, X-pipe + Corsa exhaust, so I can clearly hear how loud that setup is.

My local tuners have also said that for every AR header install they have, they have removed the Corsas because they are too loud, and they have stuck the stock exhaust back on - apparently that fixes it.

So what exactly does "fix" mean?

1) Is it the sound volume much better now? Is it for example, 30% less loud?
2) Is there any drone?

Thanks!