I found this Chip Express model for the UK :
BMW 5 Series F10 520d Diesel Tuning Box
I have no experience with these. I read the FAQ section of their site. Is it true that these chips can increase peformance and fuel economy?
They also state
"Vehicle manufacturers are forced to compromise when they set up the engine's ECU, to create vehicles which will operate in a wide variety of markets and conditions." ... is this correct?
Cheers