For many modern vehicles, manipulating the ECU is described as being anywhere from "extremely easy" to a "total nightmare". The complexity often depends on whether the restriction is a simple software cap or integrated deeper into the car's security system. Professional vs. DIY:

: Small, iterative spark changes, respecting knock feedback.

: Some ECU work also optimizes the fuel and ignition settings, which can slightly improve fuel economy even at low speeds. Cons :