But perhaps the key ambiguity in the New Perspective debate is that pistis can be translated as "faith" or "faithfulness" and in particular pistis Christou can be translated , "faith in Christ" vs "faithfulness of Christ".
Compare, for example, Romans 3.22 in ESV:
the righteousness of God through faith in Jesus Christ for all who believe.
vs NET:
the righteousness of God through the faithfulness of Jesus Christ for all who believe.
(the NET has a lengthy footnote explaining the ambiguity with references).