A clunking niose? get some one in the know to check it for u, some tyre shops do free safty checks. I can't say that a clunk in the front end of a XF is all that normal, especially not that noticable.
Stalling at Idel can u please tell me if its inject or carby??
Pan gasket leak? Can u see if it is the pan again (pan cold be bent out of shape or gasket over tightened) or is the leak from bellhousing area, extension housing, running down cooler lines or boiling out breather when stopped?
niose in LH/R wheel, I'd remove the brakedrum & see if somthing has come adrift in the rear brake assembly and is floating around in the drum. It shouldn't be a wheel bearing because it's not there all the time. sometimes a loose crown wheel bolt or a walking cross pin can make thoose nioses, but that generally sounds more towards the center of the rear?
Let us know a couple of more details & I'll try to help