Don't do it.
I reckon you'll end up modding it to handle and stop like your M3.
The 335i is a great rig if you want something that is quick in a factory package, however if you want it to turn and stop like an M car you will need to modify it.
For me, the runflats + electronic LSD (read: poobag differential) and the suspension are not good enough for what i want from a car, and when i was considering buying one after my first M3, i realised that i was planning on modding it to go/stop/turn like an M car. So i just bought another M car instead.
I would perhaps consider it if it were a 2009+ update with DCT or was a manual, but i wouldn't trade for a steptronic. Fcuk that.
2006 CS M3 | ESS Tune : CSL SMG tune : Eisenmann Race : Eibach : Tekarbon