Out of a 90 Blazer, RV cam, 30 over, flat top pistons, Question is for eintake. Manifold gaskets from fel pro, After dissassembly, there were two thin metal block off plates in the rear cooling passages (intake). When I install new manifold gaskets, it appears fel pro has taken care of them. Do I still need to install the metal block offs in the manifold? Second question, I cant remember where I saw it, but there has been some great reads about a 3 wire o2 sensor for headers using a relay. Anyone point me in the right direction?