So did you finally get to the bottom of this issue? Those two codes you stated in your previous posts "P0011 and P0021" are Intake Valve Timing Control Performance Bank 1 and Intake Valve Timing Control Performance Bank 2. Have you checked the spark plugs to see if they are okay? When was the last time you changed the oil? You know it is so easy replacing the Camshaft Position Sensor yourself, but if you want the parts warranty i can understand. But if you want to find out which version of the sensor they have installed why not take a look at it for yourself because if they have installed the plastic version it will come back defected again later. Besides the metal version is alot cheaper compared to the OE version. I hope this helps in some ways...
-Metal Version of the sensor...
http://www.samarins.com/diagnose/sen...ion-sensor.jpg
-The Original Equipment version (Plastic) of the sensor
http://www.auto-parts-online.com/upl...1282214895.jpg
-Here are the other two codes...
http://www.nissanhelp.com/diy/obd_co...11_nissan.html
http://www.autocodes.com/p0021_nissan.html