Well must say all the threads on A8 side light bulb replacements filled me with horror as I knew the day would come I needed to change a side light. It is very true the engine bay is very tightly packed and yes it not even possible to see behind the head lights....my A8 is a 2006 4.2 TDI and being twin turbo each side is an air-filter and the filter covers are a ABS plastic mouldings that form a top-hat over the filters and block all access to rear of lights both sides but this top hat comes off as it is held on by 5 cross headed screws but they are very deep down the side of this moulding, so you need a very long screwdriver.....these screws are self captive so you not lose them at the front is a moulded rubber duct but that stays in position and then this top hat removes vertically up....not much clearance any side but a little patience and its clear .......underneath is a filter....remove this and now you have total access to the rear of the main beam light where the side light bulb holder is now here was a nice surprise as under this is the power steering header tank which I had never located before.....to re-build is just the reverse....same proceedure for both sides but the power steering is under the near side and now for a joke as before this I phoned my local Audi dealer and he said sorry but to do this job the front bumper needs to come off will need your car for a complete morning ! !