Z4M coupe after-market exhaust question

[AARONM3]

I've fitted a Rogue Engineering Diablo exhaust to my car recently and it sounds awesome, not too loud at tickover but with a real howl at the upper-end of the rev range. However, I'm finding it boomy at low speeds and I think it's down to the lack of trim between the exhaust itself and the cabin.

Now I know that with a sports exhaust you will get drone if you labour the engine with a gear that's high for the engine speed but I seem to be getting an acoustic effect from the sound presumably coming up from beneath the boot floor and then being bounced around the cabin.

Outside it's obviously a fair bit louder than standard but nothing too dramatic but inside it sounds a bit Max Power for my liking and just wondering what I can do about that. The system is brand new so has probably about 30 miles on it at the moment and even when taking it out for a spin this evening it does seem to have become less intrusive.

So has anyone with a coupe fitted an after-market exhaust and then sound-proofed underneath the boot carpet and if so did that make a dramatic difference? Or is it just a case of getting a few miles on it and letting it settle?