Thanks. A friend told me it was the for a Honda Civic but the ones I kept finding didn't seem to match. However, your post spurred me to check again and after trying many combinations of search parameters, I eventually stumbled on one I think is the right one. I'll know for sure when it arrives tomorrow.
PS. The one that seems to match is for a "Honda Civic SI". Just searching for "Honda Civic Oxygen extension harness" will keep bringing up the wrong connectors.