Tremendous, not exactly. Racing or competition ECUs generally raise the power output slightly while removing alot of safety features build into factory ECUs. These safety features has the principal responsibility of preventing engine failure. And when it detects undue conditions, it runs on a more conservative mode which also means reducing power output.
ECU is not about balance, ECU tuning is importantly the most crucial component in the car. And is not something that should be ventured into unless you're absolutely sure what you want it to do and is prepared to live with the consequences should it fail. Modifying the ECU is also an immediate void of the warranty should the majority of components fail.