My x6 is going back and i have a sprint booster in like new condition. definitely makes your car feel a lot faster of the line for X5/X6
Retails for $299, asking $150
makes throttle much more responsive with three modes, normal, sport, and performance.
http://www.sprintboosterusa.com/t-faq.aspx
it is plug and play , no error codes, It only takes 5 minutes to install/uninstall so you can take them off easily prior to service, although i got services done with it on