When we install a mappable ecu in the is200, we actually decrease the fuel by quite a lot as they run far too rich in standard form, to increase power and improve economy. Optimising the fuel and ignition timing improves power by 6hp.
I do not know about and differences between the JDM and EUro models but I would not be at all surprised if the engine specs were different. To give you an example, the JDM and Euro model Supra's have the following differences ; camshafts, turbochargers, exhaust manifolds, cats, engine management, fuel pump etc etc...............
All Japanese domestic models are speed governed to 180 kph (112 mph). We fit the HKS Speed Limit Defence to overcome this, which costs £115 plus vat
Hope this helps
Mark :)