400whp will require FBO or close to it with Meth or a pretty aggressive E85 mixture...these cars will clear 400 lb/ft without too much trouble, but getting the whp there will take some more investment.
Tune (your choice)
Without Meth or E85 i'm not even sure if the above will clear 400 wheel, you'll be close but we're talking about a HP delta of about 130...that's serious. And pushing that type of power will put significantly more stress on your engine, that's just the reality of power modding. Take care of the car and it'll be fine, but understand 400whp doesn't just happen on the cheap and easy.
E88 N54 Alpinweiss/Coral Red/Motiv HTA 3586r Tial .82AR/Motiv Port Fuel/Meisterschaft Race/Berk Resonated/ER CP/Synapse/VRSF FMIC/Rob Beck PCV Valve + Cap/ST Coilovers/M3 FCA + Tension Rods/M3 Subframe Bushings/M3 FSB/AA Strutbrace/DINAN Camber Plates/Apex ARC-8/Project Kics/VAC Hubs/Rogue Transmission Mounts/Alpina TCU Flash/Icarbon/Kerscher/BMW Performance