This is the best I could do:
In sources/post.php
Look for:
if ($waction == 'preview')
Preview();
spam_protection();
Repalce it with:
if ($waction == 'preview')
Preview();
if($settings[7] != 'Administrator' && $settings[7] != 'Global Moderator' && !in_array($username, $moderators)
spam_protection();
This would VERY simply remove the flood control for admins/mods. To enable it for certain member groups. I think to have a special member group you would do something like
if ($waction == 'preview')
Preview();
$request = mysql_query("SELECT memberGroup FROM {$db_prefix}members
WHERE memberName=$username
LIMIT 1") or database_error(__FILE__, __LINE__);
list($membergroup) = mysql_fetch_row($request);
if($membergroup!="MEMBERGROUP")
spam_protection();
Where MEMBERGROUP is the name of the group to exclude for flood protection.
Note - none of this is tested etc and is off the top of my head. Also - the tabs will not work so don't try it in boardmod

Hope this helps