I tried this test program and it seems to work:
Code:
<?php
require './global.php';
require_once('includes/class_bbcode.php');
$parser = new vB_BbCodeParser($vbulletin, fetch_tag_list());
$customPreText= '[list][*]Testing[*]Testing List 2[*][color=#ff0000][b][u]Testing Color[/u][/b][/color][/list][center][b][color=#333399]How to Join[/color][/b][/center]';
$customText = $parser->parse($customPreText);
echo $customText;
What do you do with $customText after it's set?