1. Download Ralink 3070 wifi drivers for Linux (http://www.mediatek.com/en/downloads/)
2. Creat a Debian Live USB.
3. Make & make install the driver (I've changed HAS_WPA_SUPPLICANT=y and HAS_NATIVE_WPA_SUPPLICANT_SUPPORT=y inside /os/linux/config.mk but I've left HAS_ATE=n because the driver had trouble to compile otherwise).
4. sudo rmmod [module-if-exists]
5. sudo insmod os/linux/rt3070sta.ko
6. sudo ifconfig ra0 up
Finally, I've changed successfully the PID and VID of the adapter.
The 15euro wifi usb is recognised by my LE40B750, connected to my WPA2 network and I've already watched an 720p movie. Thanks samygo!!