The other intake manifold that I am running is pretty rare it's the 2nd one I have ever seen. The research I did on it taught me that it was the first aftermarket intake manifold to use air gap technology co-engineered by the late Smokey Yunick. It is almost identical to the x-celerator but the coolant/thermostat plumbing is different, 4150/4160 square bore flange only and obviously the air gap along with the lack of egr, Even though the x-celerator manifolds EGR is factory plugged by Weiand