Originally Posted by OldMan335dOwner
I am using OEM non-sports springs (base model 335d)
You can safely use OEM sport springs, but I would not suggest going with any lowering springs. It can be done, but it isn't worth it.
If you want to lower your car a bit, you can use the lowering perches from Supreme Power. I believe they'll lower the front of your car by ~1/2 inch.
Luckily, there are many other things that you can do to improve the ride.
Sway bars are a good option, as well as M3 suspension bits (tension rods, wishbones, guide rods, subframe bushings, etc...).