Yeah, before I bought my plenum I spoke to Lee and I guess they lost power or it did nothing. By the way, I could not be happier about the plenum and the results I got from it.V8Mustang said:C&L spent some time experimenting with their new plenum before building the final version. They added diffenent heights to the base of the plenum to simulate a spacer. They settled on a design that gave the best air flow and power. Adding a spacer will not help you.