i only capped off the line that ends at the center top firewall with the little rubber cap and it hasnt fallen off for 2 years. aem also gave me this small spongy filter thing that i was supposed to stick into the other line that ends near the fuel rail. i just put a small cone breather there instead. i also had a connector that i unpluged and just left hanging. i've always wanted to ask this.. you know the line that goes from the top left of the valve cover and into the intake? what would happen if i just left that alone and covered up the intake hole? i ran my car before with that hose disconected and i felt hot air coming out of that valve cover hole so im thinking that its just blowing some kinda of hot air into the intake. whats the point of that? no check engine light came on when i did this but i still didnt want to drive with it like that untill i knew what it does.