Bullshit. Carlsson was a full blown ECU (but still a piggyback) that went in between harness and stock ECU. It took care of EVERYTHING and passed modified signals back to ECU. It even communicated with automatic gearbox over CAN. I do not see anything wrong with piggy back as long as they are set up properly. What IS the difference if everything works 100% properly? We are all cheating for more power and pushing components to the limit. The only right way is leaving the car stock.
Not to trap down your idea, but why using a piggyback when you can fix parameters in the original ECU itself?
And especially why make it yourself hard putting this second sort of ECU into the car, fix wiring etc. etc. while you can use OBD for read and write the original ECU instead?
