How do you repair intake manifold leaks?

Replace the manifold gaskets.

Word to the Wise: It would help to know what caused the leak. Bolts not tightened in correct pattern or torque, or just old age? Also, if manifold is aluminum, don't gouge the gasket mounting surfaces, only smooth w/ the yellow fingers tool you can get from SnapOn, or use fine sandpaper and a sanding block. Don't polish the surfaces either, or the gasket will slip or blow out.