The TBI intake manifold is heated by a "coolant" passage that runs from the thermostat area to the rear of the manifold. This coolant exits the manifold at the heater supply fitting. There's no heater-control valve, so this coolant is always circulaing, keeping the temperature of the intake manifold as constant as possible.
If you don't have the right gaskets, the coolant in the manifold can stagnate, or even reverse-flow. The manifold will take too long to warm up, and perhaps get over-heated if the engine is run hard. There's some risk that the coolant would bypass the cylinder head and go through the manifold to the thermostat. Neither is good.
I don't know of any other SBC intake manifolds that are water-heated like this. That's why the gaskets for TBI are "special".
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I've never seen metal tabs for this application--they may exist, but I don't know about 'em. I've seen metal tabs that go into the
exhaust crossover opening in the intake gasket, but I don't think that applies to TBI engines..
