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I agree with Gary that you need to check the points gap. While you are at it check to see that they are not burnt or pitted. Also check to see that the flat spring on the move able arm has not gotten weak causing your points not to close as they should. It should take a bit of effort to open them with your finger.

To check for an intake manifold leak spray starting fluid around the manifold mating surface while it is running. If you have a change in engine speed while doing so you have a leak.