XSeries-forum

when i bought my 30d X5 the sales man said the previous owner had some sort of power upgrade done , my question is    how do i know or  how can i tell ,  it does seem v powerfull .

he probably means it's been remapped, does it fly ?

It's probably had a ECU remap, these are very popular on the BMW turbo diesels, raises the BHP from 218 to 250ish,  and the torque from 500 nm to around 550 nm, some increase the MPG as well
You can't tell unless you have the map read and compared to an original,
Some fit a tuning box which plugs into the common rail on the diesel injection system, these can be found usually strapped to the engine or under the top engine covers, and can be removed , so the car reverts back to normal.