You have a lot of options on most anything that has an OBD II port or newer. There are the Supertuner programmers that can be designed off of your spec requests or needs, and each programmer can hold several different programs that can be for different applications. So you can have one program that runs while you use HHO, or another that runs while your not. The unit will download your cars original "flash" specs, and upload another of your choice. We install them on diesel applications and plenty of beefed up up street cars. Adds a lot of horsepower to most anything. You can change shift patterns, timing, injector pulse, delete some things! Pretty cool stuff.
Almost any ECU, PCM, PCU can be reflashed but some are hard to find a program for! Others can be updated by dealers, but they(Dealers) DO NOT do alterations to the programming that effect emissions.
Its done right or its not done !
Hail HHO.