Engine Hunting.. EGR valve?

[Ngt]

Hi. I have. 2007 A8 3.0 TDI. The engine is making a hunting noise when idle and when driving. Looking at the engine I can see a solenoid flicking on and off which is making the engine hunt. having done a bit of searching it looks like it’s linked to the EGR valve? Is there a way of testing what need to be replaced? There’s a plastic solenoid valve with a grey round cap on it. Not sure if this needs to be replaced or the solenoid itself? Or anything else?

just posted a short video to show the issue. 
 

thanks

Nigel  

 

 

[Steve Q]

As you've diagnosed it as the EGR my advice would be looking to replace that.