I have noticed the "clunk" with tight turning and breaking, what can it be ?

Can you roughly pinpoint where it's coming from? Drivers side, Passenger side, behind the dash, towards the grille, etc...

drivers side front

I've got the same problem with my sl. I get it when slowly backing up with the wheels turned. Like backing out of a parking spot. One loud clunk, sounds like its coming from the left front wheel/spindle/brake caliper area.