We did a very similar thing in our old vr berlina, the intake didn't cost us a cent cos hubby acquired

some of the flexible airconditioning duct type tubing. It did make a very noticeable difference too, but we ran ours from the cutouts in the front spoiler which were pretty low to the ground so it was a real pain in the arse when it rained, we had to take it out if we were to go through any decent puddles.