Sorry I didn't realise my 1st Post had to be of a certain type! Was looking in the classifieds for a PE exhaust and stumbled across this post.
That aside, there is nothing sketchy about my post, Just giving my 2 cents. Like I said I had birds fit my 330D with a quaife LSD back in 2009, and albeit a different car, I can notice the difference, but who's to say the quaife in a 335 would handle the same as my 330D. My previous car to the 335i was an E63 M6, and in terms of what I know about diffs it may not be a lot as i don't run a race car ( and if I did it would have a plate type diff), however for street driving I have to say that I am as impressed with the M factory as I was when I first started getting to grips with my M6 and its BMW LSD.