P1416 Again!

[chiurw]

My "Check" engine light came on the other day and DIC showed a P1416.
I had this same problem back in February 2006 when my Z had 31k miles. Both air check valves were replaced. Now my Z has 41k miles and this problem returned. I know what causes this problem but how often does this problem occur, especially for a stock Z?

[No Doubt]

Since your car is stock (no headers?) the likely answer is every 10,000 miles in your case.

No, they fail for several reasons, with water in the form of atmospheric humidity being one of them.