Hi Jay,> You should know power and efficiency are at opposite ends of the>spectrum. I order get more power we need to use more energy, (gasoline)>and that takes a bigger carburetor, which is the cheapest horse power>improvement we may add, then we have add more oxygen which is in that>fifteen pound atmospheric air pressure via a longer duration, higher>lift camshaft, then we need a way to get the expanded gases out and>create a vacuum to draw the next charge in over the cross flow, which is>done with headers, tuned to 32" long, an eight of an inch larger ID than>the intake valve. This is the basic blueprint for an sixties AMC four>hundred horse.> Yes, replace the air filter every ten thousand miles.