BMW’s K46 engine has a known issue related to the Cam Chain Tensioner. Over time, the cam chain will naturally stretch. This will reduce the amount of slack and the stock can chain tensioner will apply less pressure. After about 10,000 miles a Silver Screw cap (OEM BMW part) can be fitted to increase the pressure on the cam chain tensioner. This is achieved by pushing the tensioner in by about 2mm.
When I purchased my bike (roughly 20,000 miles) it still had the factory black cap (should have been replaced 10k miles ago) and the internal tensioner spring had a gritty spring motion. It was not consistent and felt as if it was getting stuck while 1/2 compressed.
The solution is a manual Cam Chain Tensioner which allows you to adjust the lever of pressure on the Cam Chain.
It is a 1.5/10 on the installation hardness scale and can greatly reduce the cam chain noise. It will not eliminate all cam chain noise as these engines naturally make a certain level of chain noise.