I found it under the engine manifold as above described above here is a photo. Round black in center with hose attached. Hopefully that will help others. This is a 2004 XC70. Replaced valve and old cracked/brittle hoses. Cleared code. Has not returned.

This part must be the most searched for in all Volvo history. I am chasing down an intermittent P0486 (High Pressure Flow) code as well. I have the Evap Purge valve but can't find it on my 2004 XC70. I'm searched all over and can't find a good diagram of where this is. Anyone have a photo or diagram...