1.8 tsi idle engine rattle - not chain!

Hey guys got a demon I've been chasing for over a year now.

Car is a 2008 pre FL octy mk2 1.8 tsi L&K

Basically on idle the engine shakes to no rhythm and there is metallic sounding rattle coming from the camshaft area. If the N205 valve is unplugged the rattle automatically stops but the engine continues to shake. Also an intermittent "putting" coming from the exhaust. Once revs or driving the car is fine and shows no problems. The only fault code I'm getting is the intake manifold runner p3138. I've taken the whole manifold off and checked the runner and it looks good to me. I've even bench tested the solenoid.

I have vcds so any help or instructions much appreciated!