Critical to the performance of any combination of mechanical modifications is the engine management system. The key word here is system. There are many parameters of engine management that must be controlled in concert to come up with that elusive combination of high output, safe operation and drivability.
Most folks start down the ‘modification’ path with a set of chips - like the good old Autothority chips that have been around for ages. These can work well with minor mods to an other wise stock engine. Once you start swapping turbos and other parts you quickly get outside their range of control.
After that come the ‘piggy back’ systems - its their prime job to fool the stock DME computer into providing the correct timing and mixtures to support the modifications to the system. The piggy back systems can use either the stock flow meter or an after market mass air flow or some even convert the sensing system to a MAP (manifold air pressure) system.
The key similarity is that these systems rely on ‘fooling’ and 20 year old computer into working with a modified system - and you know what - some of them can do a pretty good job with the right know how behind them and (this is an important and) a sound 20 year old computer and wiring harness. The condition of a lot of the stock harnesses is less than optimal and the DMEs are known for cold solder joints creating intermittent failures and glitches - not what you want to trust your modified engine with.