Lucky M5 owners, I need your valuable input. I currently own a 91 535i, 5 speed, many upgrades and I love the car, however it stills lacks the performance I crave. I have always heard about the money it takes to maintain an 'M' series car. I've spent about $1500 in the last year on my 101k 535i for maintenance items and about $1500 on upgrades. Are M5's very expensive to maintain, meaning the usual parts exchanged because of wear, water pump, hoses, belts, fan clutch, brakes and rotors. I typically do all of the work on my, except for what I can't figure out from the Bentley manual.