You can login to Audi Erwin for an hour which I think is about 8 euros and download the wiring pdf along with other useful stuff. There are self study program (SSP) guides in pdf format available on the web. Try searching infotainment ssp pdf. SSP 435 is for 3G system but is quite hard to find. The MMI 3G optical system generally composes of an optical ring made up of Gateway, MMI Head unit, radio, audio amplifier. My MMI 3G+set up only had these modules.