An electric what you say?
Exhaust, CAI and re-tune (chip).
Get a custom exhuast. Cheaper and can be made for your needs.
CAI - I have no idea what is available for the 7 series. Maybe just a pod filter...
Chip - some say usless, others like them. Check
Powerchip I have no idea if they are any good. But they say they can increase performance by 20hp with a chip.