I know the discussion thus far has been on what you can do simply and without FI. But if you do want to go that route the options for the new M3 will be SICK.
How about 550 hp / 420 ft lb?
Someone already has obtained this with a supercharged RS4 at moderate boost. Sure I rounded up just a bit, but like I said only moderate boost.
How about 600 ft lb in a BMW V8?
How about 700+ hp in a BMW V8?
Have a look
here. Just learned about these guys but they look quite capable and professional.