I used to sell the EMI's a few years ago. After selling probably 100 sets, I stopped selling them because of problems. They started cracking and leaking after a few months. One problem that they have fixed is that the water no longer comes to the top of the manifold. If you use the aluminum risers, you need to transfer water through the joint between the manifold and riser. If you use the SS risers,like in your pic, then you must use a jumper hose to route the water from the manifold to the riser. The water holes were still in the manifold at the top, even though they didn't need to be for the SS risers. They would corrode over time and eat away at the gasket and start to leak into the manifold. They started blocking that passage off so that it no longer came all the way to the top of the manifold, only high enough to get out of the jumper hose. I use to weld them up and mill them flat before they fixed it. After that, the welds started failing in the risers and they would leak. It cost a few engines for a couple guys. I stopped selling them after that. Now, I haven't used them in about 4 years, so they may have all of the issues taken care of. I'm not trying to bad mouth them, this is just my personnal experience. I was in salt water so I'm sure that did not help. They said to stop using the polished ones in salt and go to the black powdercoat. I would use them in any application, since the polished ones have no protection from corrosion caused by salt or anything else.
I will add that they did replace any manifolds or risers that were defective. They did not pay my labor to R & R them and I had to ship them back on my nickel, but they did replace the units.
I have used several sets of the IMCO manifolds and can't say enough good things about them. They have performed flawlessly. They were quite a bit more than the EMI's and that is why I sold so many EMI's. The IMCO's may be more but they are well worth every penny. Hope this helps, Eddie.