I installed the Avin Avant 4 about 4 years ago. You need the Resler interface and IBUS app both tor OBD functionality and for the DSP to work. I'm very happy with this unit. I like that it looks just like the Nav head unit that it replaced. You will need the extension cable for the radio and DSP. You'll also want the extension for the GPS antenna wire so you can plug into the GPS antenna already installed in the car. I also recommend getting the microphone, the one built into the unit sucks. I also added a back up camera. Overall I'm very pleased with this unit.