sounds like your MAF is dirty or bad. When u drive it wont go above 3000rpms? Or does it struggle to but still make it above that? When the MAF is bad or so dirty that the ecu thinks its bad, the ecu limits rpms to 2000-2500, at least in Maximas. Seeing as how Nissans are very similar in the way they do things, maybe check that out first. Any codes? Maybe you need to clean your TB, IACV too. If the MAF is filthy, then chances are so are your TB and IACV.