In Belgium, the Z900 can be bought in 3 versions: full power (92 kW), 85 kW or 35 kW (A2 licence version). The 85 kW is purely offered for lower taxation, and requires a downtune of the 92 kW version. The dealership has to order this downtune kit from Kawasaki, which has to be registered to belong to this particular bike. In reality however, most dealerships will offer you to register the bike at 85 kW (thus with lower taxation), order the downtune, link the paperwork to your bike, but just toss the kit in the bin. Probably this is what happened to your bike as well.