knocking sound after startup
 

I'm noticing a pretty substantial engine knocking sound after startup each morning on my 2007 r56 base model. However, this engine knocking sound usually goes away after 30 seconds to 1 min.

Does this imply that the timing might be off, but that the engine management system is compensating for the knocking? A mechanic took a look inside the cylinders with a boroscope and didn't notice any significant carbon build up on the valves. It makes sense that carbon build up is not an issue on the base model since there is no direct fuel injection.

I had the knock sensor replaced recently, and before doing so, the engine knocking sound used to be much more prevalent while driving. I get the sense that after the knock sensor was replaced, the engine is able to adjust timing to avoid the knocking.