If it's installed correctly there should be no problem, I'm using vBulletin's built-in function that displays uncached templates and there are none. I suppose it's possible that modification runs before the templates for this modification are cached? I don't know.
Add this line to your includes/config.php file along with the rest of the settings then save the file and overwrite the existing config.php file on your setting.
Code:
$config['Misc']['debug'] = true;
Does the default vBulletin information say that templates are uncached? It lists templates in the footer.