Considering where the mani is cracking the bracket attaching the exhaust to the tranny is probably not the culprit.

As far as PE switching to a cast mani, I would still prep the manifold. I had a rev-hard mani(cast iron) on my 240 and there were horror stories of these things cracking. I had bought the kit on that car used and had the manifold repaired. I did little to prep it for expansion as I wasn't sure of the integrity of the manifold after the welding if I did. But it ended up cracking all the way through. I replaced it and fully prepped it by cutting the head flange so that each runner had it's own flange. I removed all cast flashings and sharp edges, particularly in the areas that would see the most stress and heat. I had to port match it as well but that had little to do with durability. The manifold was still perfect when I got rid of it. Cast manifolds tend to be more durable as their rate of expansion is lower. But it is still subject to expansion and precautions should be taken. I think the solution with yours will be to cut in reliefs for expansion.

 

The PCV valve is located on top (and screwed into) the p-side rcker cover, with a hose running off its top to the intake manifold.

It is still not very clear why the car is smoking... I took it down to a z zhop and they said that it is a turbo seal leaking. After putting on 500 miles on the car since reconnecting the PCV hose, the smoke is still there, but to a far smaller degree. There could be a lot of oil in the pipes.... who knows. Either way, my capacity to carry on diagnostics has diminished considerably up here in S.F. So, any solution that may be forthcoming, will take a long time...

Gurgen