Hi Bro,
I am glad that there is another 130i lover here. Hahaha. I love the million dollars voice of the inline 6 of our N52 engines.
I have modified my baby with the following and hopefully it could help you in the path of the poison that you wish to chance upon.
1) ADVAN RZ rims (very sweet, recommended by our beloved E46 monster)
2) AP brakes, front and rear (ultimate stopping power ;P)
3) BMW Performance front strut bar (if you are changing to coilovers, two little bars could be obstructing your adjustable pillow mounts if you are getting such a setup. add this strut bar could help understeer if the two bars are removed.)
4) JRZ Suspension (I have a DA race kit which proves to be quite comfortable for street driving. If you want a test ride, let me know. Little modifications have to been done for a race kit.)
5) GruppeM intake (still stuck in Japan)
Taking a break now and a LSD would be next on the list.
Have fun!