After the new/current A8 is rather an ugly duckling and the 7 is now for the first time more beautiful I consider the change to a used 740xd or a 750ixdrive. Both would be one of the 1st – with less than 100tkm. Are there basically known problems with both cars/engines – susceptibility? Running performance should then be over 200t and not every few months a workshop stay. Basically it is more about comfort than sportiness. (The main reason for the 7s is the appearance. A8 and S-Class fail due to the design) The A8 has been a few problems that have not really been fixed until today and there has often been trouble with the car connected with expensive workshop stays. The 750er should be clearly above the A8 due to consumption (currently 14l in average for a lot of city share) – so that it does not justify the cheaper purchase price for long. How difficult is it to retrofit an AHK? – is there a manual here somewhere? Is there with BMW a diagnostic system similar to VCDS with Audi?