In the service manual i linked you there is a whole procedure for troubleshooting it. Including checking for vacuum leaks, which is where you should start

 

http://www.nicoclub.com/FSM/G35/Sedan/2004/ec.pdf

Start on page 286

 

Thanks for your help! I printed out the pages for the inspection and will bring to dealership this weekend. I will report back on findings.

 

Have you checked your motor mounts?

 

So you never reported back - what happened? What was it ??

Thanks,

 

The dealership wanted $120 just to diagnose the misfiring issue. The problem has only happened one time since then so it's not a priority for me right now, seems to have gone away for the most part but I will get it checked out eventually.