Engine issue that has the dealer stumped?

[JefferyGT]

If vacuum is holding. It could possibly be solenoid?
Did they replace the check valve? Super easy and cheap to replace yourself.

 

[Nick408]

If vacuum is holding. It could possibly be solenoid?
Did they replace the check valve? Super easy and cheap to replace yourself.

I think the only replaced the front hub, they said the vacuum tested everything and it was fine. They obviously must’ve missed something or the problem would’ve been corrected. The amount of money they’ve spent in labor it would’ve been cheaper to replace the entire IWE system