A synopsis from Car Magazine of a CUSTOM remap - "Most chip remaps/conversions are generic and don't take account that over a car's production run its ECU may be changed and the accompanying software codes updated, so one ECU generation could have several different software codes and there could be more than one ECU generation.
It is also worth noting that manufacturers sometimes factor in an ECU reflash as part of a car's service schedule, curing glitches or improving running characterestics. This would wipe any chip upgrades, so the upgrade software needs to be re-installed. You should find out from the dearlership if a reflash was due and was installed.
One company that especially tailors chip conversion/upgrade for each particular car is Abt, based in Leeds. Abt are the German tuners who run Audi's DTM team. The work meets Germany's tough TUV standards and the warranty matches the factory offering.
On a Scirocco 2.0TFSi they acheived 40 bhp and 44 lb ft hikes to 237 bhp and 251 lb ft for power and torque. Installation time 1 hour, Cost £1299." - Ben Barry, Car Magazine, March 2010