I'm in the process of turning the TBI 350 engine in my car back from a lousy carb conversion by a previous owner to TBI, and the intake manifold gasket set I got for the original GM TBI intake manifold I'm using has the two end ports blocked of with metal rectangles with very small holes drilled in them. I've read this is to block off the two rear ports. I'm wondering why you would want to block off these ports because they aren't blocked off in the heads or intake. Should I leave the little block-off plates in or take them out?

 

Leave the block off plates. They are there to force water under the TBI unit to heat the manifold. The plates are drilled so that air and steam can exit the rear of the block.