Again it is happening at very low rpm and my oilpressure at idle is not that great..about 20psi when hot.

I need your help here because I am about to take the valve covers off and change the valve stem seals. I could in theory also change the chain guides if you think this might solve the chatter...assuming it is the chain.
I did change the chain and tensioner a year ago but decided not to change the guides because they were aluminum with rubber, worn but won't break.

Another idea what the chatter might be is: Preignition. But here I also have no experience how to recognize preignition.
Thanks, Martin