...BTW your Bieber avatar is awesome.-Malone
If you're planning on running it without a rebuild then you're probably fine in to the 150-175 hp range frankly. If you are going to bore it and install new pistons then you have absolutely nothing to worry about, just use AHU or even better ASV slugs. The differences between the AHU and the 1Z are really small. Different pistons for sure, different (but functionally identical) turbo, different stock injection pump. Early 1Z engines had a bunk ECU that was replaced with a recall, the recall included higher breaking pressure injectors (which match the AHU) and removal of the 5th injector in the exhaust. If you are going mechanical none of that matters. NO TDI has forged pistons btw, it's very difficult to forge the combustion chamber shape.The silver thing is the EGR valve...AHU and 1Z are very very similar, any performance upgrades that work for an AHU work on a 1Z with the exception of ECU upgrade chips.