Please help - p0300
 

After adding a rear fog light and changing to a GTR start button, I put my 2009 370Z in may garage for a week and drove my other car. I took the Z out for an evening drive when the Service Engine Soon light came on. I used a scanner and I have the dreaded P0300 code. Outside of a 1100 RPM idle, the car runs fine if not better.The only major modifications I have are an ARK Grip Exhaust, and a K&N Typhoon Cold Air Intake. In about a month and a half, I've tried the following:

1. Added Seafoam to the fuel.
2. Changed the fuel cap (used OEM and a new aftermarket fuel cap).
3. Changed all six spark plugs.
4. Changed all the coil packs.
5. Checked for vacuum leaks.
6. Checked the battery.

PLEASE HELP!!!