Got this done on mine today, the driver's side is SUPER hard to get on / off. While putting it back on, I messed up and ripped the air filter a bit (corner).
Should be good though, it's the part that is being pressed on near screw #7, and I super glued it back on.
As for any gains, I think it's very very minimal (less then 5 HP I'd say..). It does sound SLIGHTLY louder, but to tell you really have to have Active Sound Disabled.
