The default jetways are disabled by disabling their MODEL, so it can't be visible if they are disabled, regardless of the scenery you use. It's not very clear from your message if you still SEE the default jetways at your modified KLAX or not.
If you still see them, check other default airports: do you see the jetways ? If yes, then the only possible explanation is you haven't used the default jetways at your modified KLAX.
If you see default jetways everywhere, it means you must have reactivated with the GSX Control Panel utility, so just disable them again. This can also happen if you reinstall the simulator, but not GSX, since the deactivation happens when you install GSX.