There are companies that do that boring. There is much debate over the spacer doing any good. In theory it has the potential to increase the volume and also the velocity of the incoming air charge but it is quite small and also would only be significant at a higher speed but it also couldn't hurt the mixture. We have a member who could address that more directly as he made some spacers and undoubedly tested them. Leave him a PM and he may be able to more fully answer your questions about spacers. He is HowlerGT.