An electronic device that gives you an accurte air:fuel ratio. I ran the Zex kit on my jdm h22 in my Prelude. I didn't have any problems/issues with it. You're better off with a wet kit or pick up an extra manifold (stock manifolds can be had for $50 or less) and have it plumed for direct port. Just make sure you check your plugs after every run and have the car tuned..

-Mike