Do Red Bull Air Race aircraft make use of nitrous oxide injection?
This is from the 2014 season 

http://airrace.redbull.com/en_US/article/lycoming-engines-power-behind-air-race


  In previous years, the race teams were allowed to modify their
  aircraft, but since 2014, the engines and propellers have been
  standardised for all teams. The Lycoming Thunderbolt AEIO-540-EXP
  engine and the Hartzell 3-bladed 7690 structural composite propeller
  have both undergone rigorous testing and have performed to
  specification.


Here's a link to a smaller engine using nitrous to get 300 HP out of a 100 HP engine for record setting purposes

https://books.google.com/books?id=DhLSUHx136QC&amp;pg=PA36&amp;lpg=PA36&amp;dq=lycoming+io-540+nitrous&amp;source=bl&amp;ots=UwecpWRA8S&amp;sig=RgiMHhHnQuHJYph0TASw0Y6bB2o&amp;hl=en&amp;sa=X&amp;ved=0ahUKEwieiZTGqf7aAhVxUd8KHc5uBLoQ6AEIhAEwDA#v=onepage&amp;q=lycoming%20io-540%20nitrous&amp;f=false

and even more HP here

https://en.wikipedia.org/wiki/Bohannon_B-1