Guys - Thank You for your feedback.
I just replaced the check valve with a new one. Still the same problem.
Can someone explain to me the action an EGR valve goes through upon acceleration? Does the EGR valve open or is it forced closed? And how does the thermo valve relate to all of this? The service manual does not explain the theory of these mechanics. UUUGGGG
Or am I simply worrying about a minor problem.