Seems like there are three production 1x4 castings and an XE one. Probably 20 years ago I tested three different manifolds on the same engine. I don’t think any were the XE version. I still have the E and G but the other one is long gone along with my memory of it. There were subtle differences in the ones we had here and they all ran about the same on a 650 hp, 416 cube engine.