If it is an SDi then boost cut is the answer.
1st and second. But you'll not notice the limit.the cars are ecu limited in first gear to stop the gearbox being damaged
The torque curve is lower in 1st and 2nd to protect the gearbox. It is limited where it needs to be, which is no-where near 4k. You'd not notice it when driving, you'd need to put it on a rolling road to tell the difference I think.limited how exactly? fueling wise to avoid the torque spike at about 2k rpm??
as ive always managed to get mine to rev up to and past 4k rpm every time.
restricting the car to 4k rpm max to avoid damaging the gearbox seems a little odd as the peak torque is much lower than 4k rpm.
There is altitude compensation I think. That is why there is a MAP sensor inside the ECU I think.Sometimes they have other variables too, like ambient pressure for altitude compensation as one example but not in our case.