leave it minty - maybe only have the 1st silencer cut out/bypassed leaving just the back box - can be done at any exhaust shop & cheaply.
do a dyno test before and after in any case..!
I agree if you like that bmw tone get the. Centre box removed and get a M3 back box and a nice induction kit , I had a e36 325 with free flow at 120km on the freeway the drone gets to you.