Here are two mods that I did on my X5 35d that made a big difference
1. Eurosuperchip installed at coastline motorsports in woodland hills Cali
www.coastlinemotorsport.net. Talk to Jesse 818 222-8881. Added 50 hp and 30lbs of torque. Very noticeable change
2. Sprintbooster- instant throttle response without the turbolag. Got mine from
Turner motorsports.