Took me some time but i finally found what's causing that noise coming from head rest, when moving the headrest front/back or when pushing your back against the seat, it sounds like two metal pieces rubbing against each other in slow motion. I thought it was one of the connections in the lumbar support/headrest system making the noise somewhere lower in the seat but it's caused by two metal parts sliding on each other almost at the top of the seat, i've used silikon grease to lubricate it, hopefully it will last couple of years. To get to them, with seat still in the car, you have to take back of the seat and work your way with torch while pushing the foam to the front, it's located in the middle-top part of the seat, below are pictures of where to look for it. One of the pictures is from CDT808 heated seats mod, thanks.
Starting point after you remove back of the seat
Red Arrow - red location of the noisy part
Green Arrow - take the white hooks of the metal part so you have more room. You'll also get access to holes which you can use to guide yourself to the noisy part.
You have to put grease between two parts, between these "wings" and metal part, the wings have some extra movement so you can lift them to lubricate the space between, location is marked below
Ilustration how the seat looks without any dressing/foams