Steve, the only thing I can imagine which hasn't been covered is the possibility that the block, heads, or intake manifold were not machined correctly. Your OP stated you got the car with the heads off, so you may not know exactly what work was done previously. Your photo of the intake valley leads me to believe that the head and intake surfaces are not parallel. Now you would think that would also be a big vacuum leak, but with a closed PCV system, it might not be enough to notice. Just a thought.