335i does not have the cooling or weight advantage on the track. it is probably the worst BMW to track aside X models. Lack of LSD is another disadvantage. to track reliably you will have to install oil cooler, possibly larger radiator, and intercooler. tracking xi is even worse, not to mention that is less to be learned on the track from AWD ..in comparison to RWD dynamics.
buy e36 M3 or e46 m3. better steering, LSD, 200-400lb less in stock form, cheaper parts (e36).
pick the right tools for the job, not wrong tools that need to be modified to do the job right.
2000 M5, 161k, Ronin edition
2011 Cannondale Caad 9-5, 52mph top speed