I know how to export from belgium to the netherlands, but not the other way around.
And the sound isn't in the exhaust, the exhaust is almost the same. The sound is in the inlet side of the engine, you hear it sucking air into the fuel chambers.
The biggest difference is that the Sport engine breathes through 4 channels, where the AX GTI breathes through one. You can have the AX GTI breathing through four too, and it will be cheaper to run (uses less fuel), but far more expensive to build up. For that you will need throttle bodies.
Still, the remarkable sound of one or two (big) carbs cannot be achieved running on injection. In my opinion a four cylinder engine running throttlebodies sounds better though (they sound both extremely agressive and controlled and rev up to extremes). Listen for yourself (on a VW Lupo though):
Lupo GTI, 0 - 115 mph (185 km/h)