We could offer tuning boxes if we wanted, but can a box that alters only fuelling really compete with a remap that alters boost, timing, torque limiters, smoke limiters etc etc
Also, they are not that invisible as they throw fuel pressure faults and similar. I have tuned a BMW 123D for a BMW technician who says they know when someone has used a box due to them chucking the same faults
Another point to make is that 90% of end users will tweak the box until it smokes too much or the engine starts to cut... on later DPF equipped models, the particle filter will be getting blocked up and chucking an engine light on every 5 mins