Rattling engine on idle
 

Good evening to all Mini lovers,

I am really sorry if my thread is repeating this question, but I am struggling with this issue a long time now, and I decided to ask this community also...
So short story long... my 1.6 petrol engine (Mini Cooper 2007 - 1.6 122 hp) has a rattling idle.
It started while I was driving 130km/h on the high-way and it gave the check engine light in the dashboard, with no loss of power, and no rattling on idle.
I went to BMW workshop and the diagnose indicated a miss fire on cylinder 3, with the advice to replace that coil.
I replaced all coils and all spark plugs with new Beru ones.
The rattle is still there and no more defect detected on the diagnose.
The engine is giving all the power, and in full throttle there is no rattle, only in idle around 800 rpm it is struggling to keep this rpm. Sometimes the engine even stops in idle...
There are no metallic sounds when the engine is running, to indicate problems with the timing chain and accessories, like some mechanics suggested...
What can it be?

I appreciate any kind of answer.
Thank you all!

Thanks for nothing guys.
You are totally useless!