Yup....An intake leak would cause your issue. Without trying to be Debbie Downer, it COULD also be the corresponding surface that's warped. Did you "glue" the intake gasket on....or install dry? There are some VERY good sealants that might solve the issue. On a SBC, most mechanics DO use sealant on the intake....though it doesn't necessarily call for it.
Back in the 80's, I had a Toyota with a persistent intake problem. I took it apart and redid the intake gasket about 6 times. Got where I could do it in 1/2hr. It would last 3-6 weeks before leaking each time. At the time, the internet didn't exist. I gave up and sold it without knowing all my options. I would suggest you have an advantage...since no coolant/oil is running through VX intakes. Those fluids add to the challenge for maintaining a long-term seal....with liquid/rubber sealant. If you try a sealant, make sure you pick one rated for gasoline. I recommend you Google "intake manifold sealant" to find the most current sealants. If you haven't tried that route yet, do so.
One other thing you could do is take the intake to a machine shop and have them check it for "flatness". In Kansas City, there's a cylinder-head service/shop that has the equipment to "plane" it back straight. If you consider it, look for a similiar "machine shop/cylinder-head service" near you.
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