while I am not the brightest bulb in the pack it seem's to me that the dominator flange to 4150 flange adapter is a choke, you go from big to small then back to big, that is the system I have on my smallblock because nobody that I have found makes a dommy flange manifold for a LA smallblock,,if I had a sacrificial manifold that I didn't give a hoot about I would like to take one and weld a plate on it and open it up to a dominator flange size and see what would happen, I know it's been done but I don't have the right equipment to do it,I know, I know, we know a guy.....LOL