As previously said, best to carry out an accurate oil consumption test to establish what amounts of oil you may be burning over a period of say, 500 - 1000 miles.
However, before that, I would recommend that you carry out an oil and filter change with a genuine Nissan oil filter and proper engine oil.
Then give the car a chance to burn off the oils that may still be in your exhaust.
What cats are you running ?
Best to do the above before you start thinking about 2K + engine builds.
Alex.