Replacing a 2.5 bar map for a 3 bar one and adjusting the software accordingly isn't rocket science. Using an aftermarket ecu is much, much more work because you have to fill everything in rather than making mods to existing maps.
Btw a simple method to use the 3 bar map is with separate connectors like I did with my 147 JTD 8v.
so what exactly was altered in your map?
this is parts of a conversation with a guy who work in tuning dept at jaguar uk.
the bosch ecu's come with thousands of pages of instructions, if you buy them all at a huge cost (40k). even companies like jaguar only buy the bits they need. They work very hard on the baseline maps - the intracate bits most tuners have no idea about.
A chap who worked in this dept. at jag explained so much, jag even sent a car out for a remap (diesel) just to see what these tuner guys do. The answer from the guy at Jag was 'very little', they simply altered the basic fuel and boost map and left alone all the intracate stuff he/they were trained on and played with.
I asked him how hard it would be to map in a merc map sensor, which works on a 1volt start point rarther than the alfa start voltage of 2volts, the answer was about 3mins, providing they had the purchased the relevant papers from bosch that explain where in the map it would be, had jag purchased them - not likely, not at the price bosch charge and as it is not needed in jag, they wouldn't have wasted the money.
after this conversation it was clear that unless these papers or details regarding sections of the maps are available, there is little knowledge other than recognising the typical fuel, boost, pedal, torque limit maps etc.
yes, aftermarket ecu's for diesels are probably not off the shelf like they are for petrols. at least with petrol ecu's, there are generally at least a dozen varied maps depending on mods you can choose to start with.
I found on my alfa that the ecu would just try and shutdown and slowdown the car.
if you know a way round this and have detailed info, please share it, my old car has been damaged (front end) and is technically a write off (albeit little damage) so if you know this info, I wouldn't mind my car doing what no one else could do with it, that is, make it scream, 250bhp as a basic start point if you know how...