$new_article = new ContentModelArticle();
$data = array('title' => 'title','introtext' => 'introtext');
$new_article->save($data);
JPluginHelper::importPlugin( 'myplugingroup' );
$dispatcher = JEventDispatcher::getInstance();
$results = $dispatcher->trigger( 'onContentAfterSave', array('com_content.article', $data, true) );
print_r($results);
onContentAfterSave event for custom group plugins. It should be
content group.
Dmitry