Unfortold "Carb Spacer" Power?

I'm running this one on a 390 in Nikkis 72 F100 with a single plane Streetmaster and it works great. I ran it for a few miles with out the 4 hole piece and it stumbled all over the place and was a dog. I put in the 4 hole piece and that truck has the smoothest acceleration I have ever felt and will boil the rear tire off if you don't foot F it.