iTunes WILL interfere with the connection, and when it is not interfering with the connection it is causing latency issues along with dropped UDP packets.
It is NOT a process you want running in the background on your computer, EVER.
I cannot stress this enough. No matter how you think it is not impacting your game play, IT IS! It is the nature of the beast. It is why I listed it as one of the number one things to do when you have connection issues. KILL IT!
Wireless is going to be impacted by the phase of the Moon as well as Sun spot activity. It will never be consistent. It is also the nature of the beast.