(bit long but interesting ;)
I been having a whale of a time sorting issues on the 540 the last few months, after a gearbox rebuild which saw new guibo and centre bearing we spent 4 weeks trying to find the rumbling at low speeds, I initially pointed the finger at the Miele centre bearing (yeah I know I never use the brand if I can help it) I got the shop to put the original bearing back in, lucky I kept hold of it, that fixed the rumbling surprise surprise...

Anyway the other issue i been posting about over the last year, the cutting out when cold and accelerating, I reported in the other thread about finding the fix, I got the shop to put the crank pulley/dampener on while they were swapping the bearing back, it drove smooth before it went in, it got the shakes after I picked it up that night, next day it was baad, got worse during the day to the stage its at now where the front end feels like its going to come off at 50-55mph!!

Control arms almost new, all joints are tight or 99% tight, idler arm on steering is worn, a mm or so play, caster bushes were done 50K ago but not sure if genuine, they were the green centered ones aka 750i bushings, I can move the arms back and forth on the bushes by hand, have to use fair amount of elbow grease mind you.

Would it be fair to say the bushes were starting to go and being up on a hoist for hours on end many times over the last 6 weeks has pushed them over the edge?? Or am I missing something here?

I rotated my 17" wheels front to back, no change, cleaned front brakes and cycled the pistons in and out 3 times to make sure they were moving smoothly, my last job tomorrow will be to put the old wheels back on and see how much it changes the vibration and if it changes it, then its back on the hoist to try and find what the hell is going on!

Any ideas or suggestions I have missed PLEAAAAASE speak up guys!