Quizas esta parte:
5              else if($depth == 3)
 216              {
 217                  if($donecount < $mybb->settings['subforumsindex'])
 218                  {
 219                      $statusicon = '';
 220  
 221                      // Showing mini status icons for this forum
 222                      if($mybb->settings['subforumsstatusicons'] == 1)
 223                      {
 224                          $lightbulb['folder'] = "mini".$lightbulb['folder'];
 225                          eval("\$statusicon = \"".$templates->get("forumbit_depth3_statusicon", 1, 0)."\";");
 226                      }
 227  
 228                      // Fetch the template and append it to the list
 229                      eval("\$forum_list .= \"".$templates->get("forumbit_depth3", 1, 0)."\";");
 230                      $comma = $lang->comma;
 231                  }
 232  
 233                  // Have we reached our max visible subforums? put a nice message and break out of the loop
 234                  ++$donecount;
 235                  if($donecount == $mybb->settings['subforumsindex'])
 236                  {
 237                      if(subforums_count($fcache[$pid]) > $donecount)
 238                      {
 239                          $forum_list .= $comma.$lang->sprintf($lang->more_subforums, (subforums_count($fcache[$pid]) - $donecount));
 240                      }
 241                  }
 242                  continue;
 243              }
... quizas antes de esto:
if($donecount < $mybb->settings['subforumsindex'])
Algo como esto:
if($forum['fid'] != 135)
{
continue;
}