I'm also wanting to remove NEI from my client and server, so that myself and others playing on the server cannot see/access the NEI item list on the right-hand side.
I've changed both modloader.cfg files for the server and client to mod_NotEnoughItems=off, but can still see and access the items in-game.
I've also changed NEIServer.cfg permissions with no effect.
I know that you can press 'o' or hide NEI from the option menu in-game, but ideally I'd like to remove/lock-down/hide the NEI panel from players logged into my Tekkit server.
Any help would be appreciated!