Hi!
What is it you want to know?
Todays .40 sport engines are more or less equally when it comes to power in a sport airplane.
For straight out power, in pylonracing, running 80/20 fuel and a 10x6 prop, nothing beats the Webra .40 GT! Thats the engine of choice over here in Sweden in Q-500 pylon racing and has been for several decades.

Runner up is the ASP.40 (Kyosho .40 GX) which is a very good engine when it comes to swinging large props. It can handle a 12x6 APC without problems.
Both these engines swings a 10x6 RAM or Graupner at around 14000-15000rpm on just 80/20 fuel.

OS FX .40 , TT.40 PRO SE and SK .40 are also good engines and are very userfriendly, and they all turn the 10x6 RAM and Graupner props at around 13600-13800rpm.

Sadly FOX .40 engines are no good compared to the above engines.