Cobb Accessport Bmw V2 Ap-bmw-001 on 2040-parts.com

This unit is used and in good shape. It is "unmarried" from my ECU and ready to be engaged in your BMW. If you have a BMW 335i, I already have all of the MAPS downloaded to the COBB Tuner (otherwise you will need to download the maps from the Cobb website, free.).

The Accessport V2 is the world's most flexible ECU upgrade solution for BMW. Unlock power hidden within the vehicle by replacing conservative factory settings with more aggressive calibrations. Upgrade forever with off-the-shelf (OTS) calibrations for most bolt-on modifications. It's the last engine management solution you'll ever need.

All of COBB's tunes can be downloaded free of charge from their website if you wish to add more to the unit.

This thing will really wake up your car and make driving into a much more fun experience.
Also, reads trouble codes and can be used to monitor your car's performance and display gauges (I like to use it as a boost gauge)

There are a multitude of you tube videos help guide you through the use of this device, although it is pretty straight forward (Plug and play).