There is a turbo kit for the 1.4 AEX engine, its a German site i forget what its called but its for the Polo 6N engine (same engine)
Stock internals will run low boost with different pistons or stacked gaskets but the AEX engine on turbo boost needs to be revved quite hard (usually raise the limit too as its a low revving engine) the turbo tends to use the bottom end torque of the AEX engine and then boost above it so it pulls hard to the red line, but due to that the stock bottom end etc.. wont thank you as they don't like heavy revving and under heavy boost it really wouldn't like it, also all the fuel system would need changing/customising, Your talking thousands for the kit and engine rebuild.