Before getting another manifold, try the RTV and a second pcv. Let the sealant cure for 24 hours before starting. I would also tie in a vacuum gauge to the intake manifold vacuum source, and, if you can rig one up to the crankcase, use a gauge to check the pressure there. I agree, the second pcv should be a big help. It is possible to get two bad intakes, but I doubt if it happens very often.
