Just as a warning all the engine management system for the Mazda3 are either cheap or effective, but not both. The Microtech runs about $1400, and I don't know much about the Haltech units but from what I can tell they aren't far behind.
Most (well, pretty much all) piggyback ECUs just don't work on the Mazda3; the stock ECU eventually overrides them or just gives up and goes into limp mode.
Most (well, pretty much all) piggyback ECUs just don't work on the Mazda3; the stock ECU eventually overrides them or just gives up and goes into limp mode.