So... the engineers comply.

I once had an engineer come to me saying that he was being victimised by other engineers about a technical solution. I took my most trusted engineer and asked him to independently review the code. He came back and said the code was crap and needed to be rolled back. We rolled it back, a code walkthrough was performed on this code and we went into testing. When that function failed, I approached my most trusted engineer. My translation of what he said it "I didn't like the guy"... So, I've learned that even great engineers can be compromised, despite many claims I see on the Internet.

Regarding Porsche's knowledge, I agree with another poster in this thread who said that Porsche may have tested the unit in the conditions that didn't show the emission problems. Without further information, i'd give Porsche the benefit of the doubt.