Originally Posted by Jeff@topgearsolutions
I'd recommend this also. If you are definitely getting downpipes I would wait to have those on first, they change the sound for the better and might be enough as is.
I can tell you that you likely dont want to go with a simple muffler delete as it will drone like crazy and likely be very raspy.
Some people have changed their mufflers to something like vibrant,magnaflow, and even flow masters with interesting results. I dont have any specific videos though, sorry. Anyway, everyone has different tastes in exhaust, and I just want to mention it's hard to get this car not to be raspy, as inline 6 BMW engines historically always have that raspy chainsaw noise. Of course the turbo's nowadays muffle a lot of that sound. If you hear this exhaust with the wastegates open, N/A mode on some tunes, you can hear a resemblance of E36/E46 sound characterstics.
Long story short, done delete too much yet, wait for downpipes, then if anything replace stuff with resonators to smooth out sound.
Downpipes on an E90 exhaust does absolutely nothing by itself. Still quiet as a damn Lexus. The E92 exhaust doesnt have resonators so downpipes would do quite a bit.