If your car runs on 2 types of fuel (usually gasoline and gas), the TUNE USB version is recommended. With this version you can easily switch between two curves: curve 1 is the standard to which the yellow wire is not connected and for curve 2 you connect the yellow wire. You can, for example, install this in such a way that the contacting of the yellow wire with the distributor is controlled via a switch in the dashboard.
Attention point for the TUNE USB version: the connector for the plug is fragile.

In all other cases we recommend the TUNE + Bluetooth version. This has the great advantage that the curve is very easy to change using the app on your phone or tablet. Great if you want to regularly "play" with the curve because you are driving a rally, for example. But also if you have a modified motor or a motor for which no standard 123ignition with the correct pre-programmed curve is available. In those cases you can probably do well with a fixed curve. Even then you are well off with the Tune + bluetoot version, because via your telephone you can read all kinds of measurements from, for example, the speed and the engine temperature. Moreover, there is an anti-theft option on this version.
Attention point for the TUNE + Bluetooth version: the software is regularly updated, which means that the app also needs to be regularly updated