Extra time scandal
As sourced from The Guardian. The link presents the evidence that Man Utd get more injury time when they are loosing compared to when there are drawing or winning. 
The Guardian has looked at all of United’s league matches at Old Trafford since the start of the 2006-07 season and discovered that, on average, there has been over a minute extra added by referees when United do not have the lead after 90 minutes, compared to when they are in front.