[tbworld]

1.) Open AdminCP.
2.) Plugins & Products -> Plugin Manager -> Add New Plugin (very bottom of the page)

Fill in the following:

Product: vBulletin
Hook Location: showthread_complete
Title: Nullify Poll in Showthread
Execution Order: 5

Plugin PHP Code:

 
// if ($pollid == 3)  // Uncomment this line for a specific poll ID.
{   
   $poll = '';
}

Plugin is Active: Yes

Click Save.