It is about circumcision and the ceremonial works:
Ephesians 2:11 [ Jew and Gentile Reconciled Through Christ ] Therefore, remember that formerly you who are Gentiles by birth and called “uncircumcised” by those who call themselves “the circumcision” (which is done in the body by human hands--
Paul is explaining how it is no longer by the works of our hands, as the way it used to be.
No, Gentiles had nothing to do with the circumcision. Even Abraham was accounted righteous through faith BEFORE he was ever circumcised.
Paul is making it clear that salvation has nothing to do with works of any kind.
Romans 4:9-10 Cometh this blessedness then upon the circumcision only, or upon the uncircumcision also? for we say that faith was reckoned to Abraham for righteousness. How was it then reckoned? when he was in circumcision, or in uncircumcision? Not in circumcision, but in uncircumcision.
Circumcision was only a sign of a Covenant....a seal and never made anyone righteous, and was not a work of righteousness. So your insistence that Eph. 2:8 is speaking of that is ridiculous.
Romans 4:11 And he received the sign of circumcision, a seal of the righteousness of the faith which he had yet being uncircumcised: that he might be the father of all them that believe, though they be not circumcised; that righteousness might be imputed unto them also: