Almost nothing. It's just not worth modding one besides some really basic stuff. It's too expensive for the gains compared to a turbo car. Anything from a 350z motors will fit them, so you can go nuts, but realistically, most people are happy to have a bit more noise and breathing. I don't want to give a power figure, cause whatever dyno you go on will be different.
If I was to "finish" mine, it would have high flow cats and a uprev tune. No cams or headers. Mine currently runs 94mph, I think it was, down the 1/4. Compare that to the nm35 numbers in relation to power.