I have a 2002 540i M Sport and the guides gave up at 185k. My wife pulled in the driveway and I heard that chain slapping and knew it was time. Pulled the oil pan and there were lots of small plastic pieces. Pulled the valve covers and found big pieces wedged between the chain and the block. You replace the cam chain tensioner when you do the chain guides (like doing the cooling overhaul). When I took off the upper timing chain covers, I could see where the loose chain had started eating away at the back of the aluminum cover.
No thats oem tensioner at 170k.. Thats y i figure it wud help a lot replacing it.