To start off, I'd like to say that I've done my research into this topic on multiple forums, from multiple sites.
Drove to work today and I found my car idling very rough at red lights. The whole car was slightly shaking, and the RPM's would drop lower than average at points. As soon as I stepped on the gas all odd noises went away and the vehicle ran smooth.
When I parked, the rough idle continued. Although I DID NOT HAVE any SES lights, I decided to scan the ECM with my OBDII. Got a P0300 and P0021 code.
I know the P0300 is a random, multiple cylinder misfire detected and the P0021 (for nissan/infiniti) is the intake valve timing control solenoid on bank 2. I'm looking for suggestions from people that have had similar issues. The following are some maintenance items I have done that could be related to this issue.
Changed the spark plugs 20,000 km ago (used OEM platinum tipped spark plugs, gapped correctly).
Cleaned the MAF sensor and throttle body twice (last time I cleaned them was in the summer, over 5000 km ago).
Fixed a vacuum leak in the summer when I replaced my air filter; I can assure anyone there is no vacuum leak.
I have put a total of 4 bottles of Redline SI-1 fuel system cleaner through the engine, with the last bottle ran through about 400 km ago.
Regular oil changes with Mobil-1 full synthetic oil, and I am always sure to keep the oil level at the top.

Only issues I have had with my G is axle related; I have never had a single odd noise come from the engine, let alone a hard misfire. I drive the car every day and have never experienced any odd symptoms as I pay close attention to its operating condition.

I have heard some issues were fixed by realizing that coil number 4 and 6 were accidentally swapped; this is not the issue as I am sure I replaced the plugs correctly, and I have gone over 20,000 km without an issue.
I have heard some issues were fixed by replacing the camshaft position sensor; this seems odd to me as I am not getting a code for any camshaft sensors. However, any input on this would be appreciated.
Finally, I have heard that resetting the ECU has "miraculously" solved the issue. Although I don't like this method, I will try this and see what happens.

Thanks in advance people!