The primary change is not only the larger tubing, but also losing the restrictive factory setup and going with filters that flow 2-3x as much air.

We used stainless to weld the y-pipe and bent aluminum tubing for the rest.

It flows so well that when I got it, I put my hand in front of the grill and could feel the thing sucking air at idle, something I never felt with the factory setup. I have no idea what kind of gains I get, but after extensively modding 2 XFs, the gains are pretty severe for an intake. I would put it in the same ballpark as getting a tune, nice gains either way. Good luck.