This is why you have Super Moderators in your board.

If you dont want your admins to access "admin only" features, simply change their group to "Super Moderator". So they will be able to do any Moderator actions in any forum while they cant modify admin only options in Admin CP.
Anyway if you dont like the idea, this is the code you should insert to any relevant part in your vbulletin code that you dont want their access:
-- cut --
if ($bbuserinfo['userid']!=1)
{show_nopermission(); exit}
-- cut --
Insert this code before the part that you dont want their access to any script.
Enjoy..
Logician