I have a 2003 350z that I bought 2 months ago and I have placed a new Injen CAI on it. After installing it I have had a trouble code come up P0304 and I have cleared it only to have it come back after 200-300 miles. I have replaced the spark plugs, moved all the coils to different cylenders (to see if that was a bad coli and code came back the same) added fuel injector cleaner also. Could it be a vacuum leak?
Thanks in advance...

 

Check the PCV breather hose but that's closer to cyl 6 so I doubt vacuum leak. Check wiring harness, do compression test.

 

Thanks for the advice.. Ill check the PCV hose tonight along with the wiring harness....

 

P0304 is a generic code for misfire on cylinder 4; did you see oil on top of the plug when you removed it .. possible short in wiring if you have already moved the coils around ..