My research has shown me that it uses slightly different internals. Apparently they are made to with stand a little bit more then the GTX. Also, it does run a little more boost. The 323 GTX runs like 6-8psi stock. Most of the 323 tuners tune up to 10psi. Apparently the ECU has a hole in the fuel map at 10.5psi, so they add a chip to get over that. The GTR I think runs 12psi stock. The ECU is already corrected.
check this out though, your GT or BPD has forged internals ! Believe it or not the internals are meant for some power. Dont be afraid of putting a strain on the internals, because more then likely you´re going to blow the head, or the block before the internals go. Unless you spin a rod bearing or something like that. The biggest difference is the compression ratio. If you want to run boost you want a ratio of like 8.2:1 like the GTX or 8.0:1. With a ratio like that you could run like 17psi on pump gas, and not much change in timing. With some race gas and timing control there´s no reason why you couldn´t hit 25psi or so.