You can alter the aircraft.cfg's power scalar from 1.0 to 1.2, but this will also make the model fly faster than historical specs through its entire performance envelope. In other words, it'll be a little hotter than you may prefer overall. This side effect may not be what you prefer.
You can also add WEP to the engine in record 505 by opening the air file of a Hellcat or Corsair and copying the war emergency power type, manifold boost and boost gain values from their record 505 area. This also may not authentic, but it gives you an option that's more selective in usage and it doesn't affect the entire horsepower range of the engine throughout the flight session. You can choose to only use WEP on short takeoffs and keep it deactivated for all other flying. And unlike the former option above, it won't affect AI performance either. They don't use WEP at all, but they are affected by power scalar bumps in the cfg.