i have a 535 5 spd manual and have driven two e34 540 six speed manuals and one e39 540 six speed manual.The std 535 has 155 kw and the 540 has 210 Kw has a big difference and even though the 535 is quite tourquey the 540 is(and feels) much faster and more civilised which is to be expected ,the M30 engine is old by comparison.The v8 may use LESS petrol than the 535 but is harder to work on(less space) and more spark plugs and more oil.The initial models also had some issues withthe nikasil bore coatings,not all markets were affected.In my experience the 540 does not actually feel quite as responsive the 535 esp in steering and braking.You need to drive some,but once you have driven a 540 ..