The B58 engine that comes in the 40i (in this case the M140i) has huge potential for big power. The current problem we're facing is that only map 1 on the JB4 is available due to the fuel system not being able to cope. The graph below will show what a JB4 on map 1 only can do. We have tested cars with map 2 and they've produced almost 440 bhp but the AFR was too lean until there is a fuel system upgrade available.
For now though, over 410 bhp from a simple stage 1 tune is more than enough. Especially with over 630nm of torque!
Power gained: 47 bhp
Torque gained: 124 nm