Did you have the #2 cylinder missfire code prior to giving it a tune-up, & did you erase that message? Also, with that message it could of been a really worn-down plug or a bad wire on #2? Hopefully, it isn't what Chris is mentioning, but like he says, "a compression Check" would verify this, before you start dumping money into parts. Also, your coil pack could be bad for that cylinder? That's easy to check with an ohmmeter.