I wish I had the Eisenmanns on, too.
When I first got my Eisenmann Sport, the first 20 miles or so it was quiet, and gradually got louder and dronier at the same time. After 300~400 miles, the drone lessened to the point where there's very little drone left. Prior to that point, the drone was so nasty that made me want to switch back to stock mufflers.
The loudness did gradually increase during the initial 1K miles.
I've sat in a friend's E46 M3 with Eisenmann Race that were fully broken in. It was much louder compared to my Sport. And very drony. My friend eventually couldn't stand the drone and replaced them with Borla's. How many miles/km's ago did your friend install the Eisenmann Race? I'd say give it some time and it should sound louder.