N15 is the Almera chassis number, e.g. K11 Micra.
GA16DE is the 1.6 engine used in the Almera and Primera, I believe.
I'm not 100% sure, but I think the Pulsar is like the imported version of the Almera?? Correct me if I'm wrong! The Pulsar GTiR is the SR20DET, but the Almera GTI is the SR20DE.