I've said it before, and I'll say it again. The 2003 cars will only produce about 255hp at the fly. For some reason (and it may be because Nissan have exaggerated) the engine underperforms by 10%. My car is only 255ish, and I've seen several other people post similar figures.
This was posted a while back by martinmac, and supports this theory...
http://www.rri.se/index.php?DN=29&List=M-N