Hi I am getting a P0300 code on a 2005 Nissan Maxima with the 3.5. Cleared the light once and came back within a day, it also sometimes blinks. Replaced all spark plugs and air filter. Only symptom was a somewhat rough idle which pretty much cleared up once the plugs were changed but the P0300 still came right back. What else should I try? Thank you for the help.