3" drop is a LOT. Didn't even know you could go that low. Realize how much an extreme drop is going to compromise the driveability of your car - getting into driveways, speed bumps ... and it will especially suck in the winter. I would go for 1" front and rear to start, then lower as needed. 1" drop looks good on these cars.
2011 BMW 335i E92 - Le Mans Blue, 6MT, M Sport. JRZ RS Pro, Quaife LSD, BMW Perf Exhaust