He's mistaken. Not sure who you called, but there are a couple who really profess to "know" a lot, and they are simply putting a huge emphasis on certain aspects of a build. You'd be hard pressed to get an Airgap to idle rough on a 318. The Crosswind has smaller ports, both in length and volume, and the casting quality stinks. So a rough idle can be from poor fitment, or porosity, or port mismatch. The one I tried seeped coolant out the rear corner of the casting, had poorly tapped holes, and was a very brittle aluminum when you did try and tap it... There are reasons they are half the money, and it's not a perfect copy as some suggest.