It's easy to make gains on a 1zz with extractors, 2zz is a lot harder. Because its already "up there" in terms of gains so to speak ????? There are gains to be had if significant R&D is put in, ala the TRD extractors and PPE race extractors. But porting the factory manifold is the best value for money. Many others have tried, and failed, to make power over the stock manifold. Will the headers for Celica GTS fit the stivo? Or the Matrix XRS (2zz-ge) ? or the RunX ?