I have a conley's performance car in my sideyard. It does not have a spacer on it. I often wonder if it helps these cars as a large spacer helped a carbed car when I raced dirt track cars. I have a older hemco upper on my car and was going to throw it out but after hearing steve tell me they are good pieces I will keep it. It just looks like it forces air into the center on the intake not using the whole upper port area.