[Fanis]

You have some valid questions and I will try to answer them, based on my personal thoughts and little knowledge I have.

Firstly, there are 2 major tuning options (or schools if you like): Remapping the existing ECU or installing a tuning box, which in affect is another ECU working in parallel with the factory ECU. The remapping means that the engine map (i.e. Air, fuel, turbo pressure etc.) is changed to increase power and torque. The tuning box, in effect alters the singnals of the sensors feeding the stock ECU, so it alters the values of these. Both have the same effect and it depends on how good they are designed and programmed, in order to achieve the increase in power and torque without sacrificing the delivery of this power. For example it is uselles to gain +100bhp but only for a 1.000 rpm span...it is better to gain +50bhp, but be available throught the rev range.

1. There is no sorcery involved in the tuning boxes. Just plain programming...quie simple to do, quite difficult to achieve the desired results.

2. With turbo engines, it is easy to get an increase at bhp without changing anything in the engine, by just increasing turbo pressure and fuel burned. Up to a point is easy and quite safe, without any other changes. Above a percentage (%) of an increase, it is vital to upgrade other componenets as well.

3. BMW offers their own tuning solution, through M Performance products.

4. BMW cannot offer big power increase, mainly due to marketing since it may "steal" sales and prestige from the more expensive models.