HI!
I would install a fuel pressure gage and monitor the pressure when its running bad to see if it drops , one more thing to check would be a restricted exhaust system building up pressure while driving will cause a loss of power and poor running . This is what I would check next, Thanks let me know if you have more questions, ROY!
ASE Certified Technician
Nissan Master technician
OK!
Thanks a lot , let me know if you need more help in the future and good luck ROY!