iv had 2 made 1 for my mate escort and 1 for my 3dr we have put the 1 on the escort and my mate said it feals a lot smoother . i would say they do work as when you stip the manifold down you can see that theres not that mush room inside for the air to get into the trumpits so the more room you give them has got to help the air flow.

The photos are of a 2wd inlet but im putting a 4x4 on my 3dr as they are bigger inside and have better flow frow the neck