I have been having an ongoing issue with a P0300 code with my 2005 G35 AT Sedan and I am beginning to think my problem is due to a faulty ECU. A quick rundown my engine has passed compression tests, leakdown tests and I have had all spark plugs, and fuel injectors replaced twice, and also had my wiring harness replaced. So this is why I suspect the ECU.

I purchased an ECU for a 2006 AT sedan because it was the only one I could find at the time, and the dealer installed it and my car ran normal for about 1 week and then it was right back to misfiring. The dealer said they think the issue was that the 2006 ECU code BM was not a perfect match to my existing2005 Code ECU L7, and that it wasn't holding the tune.

Here's where things get really confusing my car is an 2005 but according to this document I found on http://www.automotivetalking.com/inf...st-2007-a.html

G35(V35)
CODE Part Number Program ID UpDate Vehicle Description
BM MEC-65-210 AC700 2005 INFINITI G35 5AT (SEDAN)
L7 MEC-35-210 AC300 2004 INFINITI G35 5AT (SEDAN)

As you see my 2005 came is using a 2004 ECU. Should I buy an L7 and see if that fixes the issue, or are the ECU's compatible and not the real issue.