I'm in your exact same boat. I have a 128i with the N51 engine, so it's got the upgraded intake manifold from factory. Sounded way too quiet, so I deleted the secondary cats and resonator but kept the stock muffler. Now the exhaust SHINES. Zero drone under normal throttle, can hear some burbles with the top down. Really woke the car up. Give it some gas from 1.5-2.3k RPMs and it sounds MEAN. I love it now. Still aiming on making it louder.
