Antonio,
All V Pros are standalone, not piggyback. Even if you use it with the factory ecu, that doesn't mean that it's piggyback. The V Pro has its own basemap and disregard the factory ECU map. You can buy the 'ecu-less' harness from HKS to remove the factory ECU but wiring the aircond would be a nightmare, that's why the factory ECU stays.
As far as I'm concerned, you can't buy a V Pro that is specific for a car. All V Pros are sold untuned and you need to get it tuned by an authorised HKS tuner. Only HKS Japan and HKS Thailand can give authorisation.
Talk about cost of the unit, mine just got stolen recently, and I heard some joker bought my stolen unit for RM2,500.