[USMCrebel]

this is going to be a very very rough explaination, but here it goes.
the intake on the mach is kinda crunched real close to the engine, and when the air goes in, it's really tight, and "restricted". So the intake spacer add's a gap so more air/ more cool air can flow in easier and thus becoming less of a restriction on the engine, and forcing the better air in allows for more hp/ tq to be achieved.... and it gives you better power thoughout the power band, so even though your peak gains aren't much, 4-7hp and 15-20 ftlb, this is an increase in the WHOLE rpm range.

wow i really butchered this with my limited understanding, but thats the kinda sorta way it works and what it does.