I sold my N3 and got the N4 I was wondering if I can use the same harness that plugged into the N3 or do I have to change everything? Thanks

Change one thing- the rca connector. I think the N4 is bigger, and you will need to do the same thing like a D3 (remove and insert a wire) for the bypass. Here is a link to the bypass page-

http://www.avic411.com/forum/viewtopic.php?t=10089

Scroll down a bit for some pictures. Hope this helps.