NG Thrust Ratings
If your engine has been de-rated to 20k it will never deliver more than 20k as the EEC will limit N1 to provide 20K.
The only way to get more out of the engine is to up-rate it.
To change the thrust rating of an engine the EEC/HMU/FUEL PUMP/ENGINE ID PLUG/LOADABLE SOFTWARE all need to modified and or changed depending on mod status and part number to change the thrust output of the engine.