I fitted the M Factory Helical LSD to my E92 335i 2 weeks ago and so far so good. It took me 5 hrs start to finish to fit (bolted diff), and was really straightforward.
As for the difference it is night and day. The car no longer struggles for traction and it makes for miles more fun in the corners! Its also very quiet, probably more so than the factory diff.
I had a Quaife lsd fitted to my older E90 330D (still 320Bhp/700+ Nm) and I have to say the M factory is superior; Overall the car is miles more predictable!
I didn't make my decision based on price either, Just was disappointed with my Quaife last time and fancied a change and had been recommended the M factory from a couple of guys I know who race hondas.
I do not work for of have any affiliation with M-factory and realise the mistake in this being my 1st post!!
Last edited by Birnie85; 03-06-2014 at 04:02 AM.