Help diagnosing engine noise

Hi all,

I've recently noticed my ASZ code engine start to make a knocking sound when revving. It's coupled with some clattery vibration which can be felt through the controls. It started pretty quiet a few days back and has progressively got worse. There's a little bit of black smoke but the engine is at 240000 now and is about due some fresh oil too. I've taken it to a mechanic but they're not sure what it is for certain. They say it may be the EGR, it may be the injectors or it may be the turbo. My fear is that it is cam wear, personally. Just wondered if anyone might have an idea what it may be? Any common failures on engines of this age?