2001 pathfinder code 1320 again:(

so.. I Bought my 2001 pathfinder used at an auction. On the 7th day when the warranty was up it started to shudder and ses light flashed and stayed on. Long story short, I changed all 6 coils as recommended by Nissan. One month later guess what? Same thing happened again! This is the SECOND time that I got 1320 code. This time he it says coil 1 misfiring..:/. Why??!!! Something is causing these things to fail. He says he thinks it isn't a bad coil already. My question is, if it isn't coil 1, then WHAT is it?? How much money do I need to keep dumping into this pile of garbage? Does anyone have a solution? I can't afford to keep it, nor do I want to burden anyone else with this issue.
Btw. It shudders sporatically and on the highway sometimes it jerks and acts weird.
Thoughts..?