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First, inspect the engine compartment for any loose/broken vacuum hoses. If OK, spray carb/choke cleaner on and around the EGR valve and the intake manifold area with the engine at idle. If the engine smooths out while you spray a particular area, you have found the source of the stall.
I'm sorry, I hadn't noticed all the mods. In your case, distributor can only be set on basic timing. Cam lift and duration will determine how high the idle speed needs to be to prevent stalling. Didn't your cam come with those specs?