EGR Codes P0401 and P0402 on my 2.7

[rkntoy]

Just had to swap my head - even though I kept up with valve adjustments it still burned a cylinder 1 exhaust valve coming back from Ouray.

Started with throwing a p0301 which made sense to me. Then, right before swapping heads it started throwing both p0401 and p0402 codes at the same time. This did not make sense as how can you have excess and insufficient flow at the same time. Well after swapping the heads good old p0401 and p0402 popped up again after driving for about 15 minutes.

Thoughts?

 

[rkntoy]

No one has a comment? I thought I would at least get one reply telling me to tighten my gas cap.

Think I am going to start with vacuum lines.