Best answer I can give you ****** is....that depends...
The idea is that the spacer increases the plenum size, and as a result torque.
An older engine may feel the increase, but for newer engines there is little effect.
The parts with the spiral machined into it, is supposed to make the incomming air swirl. However if it is a double throttle, like alot of Ford engines the 2 swirls would clash with each other and just make turbulance.
The idea of increase performance is to get the air and fuel in and exhaust out as fast as possible. That's best done with smooth passages, then mix the air and fuel just before ignition. I don't think the spacer does much for that. It may help an older tired engine but that's it.
Maybe spend the money for something else, like an electric fan, to free up some power.
Maybe some others can give us more insite.