[335dFan]

I also have the base model suspension (2011 E90 335d). After driving my new (as of May 2012) "d" I felt the same way about the suspension, not so much about the steering. Maybe I didn't notice it. So, the first thing I did was a conservative, although expensive since I didn't want to install myself, upgrade by replacing the four dampers with Bilstein B6, OEM height. It made a big difference, at least to me, in getting rid of the wallowing and small road imperfection jostling. I was reasonably pleased with its track performance at Summit Point Jefferson Circuit. The limiting factor was me, not the car.

But after driving a friend's Sport package and M-Sports "d", I know what the car can feel like, and so I have the itch. ALthough not finally decided yet, I am leaning toward an all BMW-parts upgrade using a combination of BMW Perf kit and M3 parts, including sway bars and maybe also a strut brace. Am also strongly considering a rather expensive Quaife LSD installation to replace the open diff. Tuning will come somewhere in time independent of the suspension work. But this all won't come cheap, so the budget constraints are definitely a consideration for upgrades.

The part that I am still uncertain about are wheels and tires. I have stock 17x7.5 (I think the 7.5 is right) and OEM all-seasons, although now I have BLizzak LM-25 RFT's mounted. When spring comes back in a few months, I need to decide on whether to go to different wheels. I didn't really want to mess with more expense, but it seems most of the really nice wheels don't come in 17", but frankly haven't done much research. I want to get all the mileage out of my OEM RFT tires that I can, and they only have about 8k on them at the moment.