I have a 2007 Infiniti G35 Sedan with the VQ35HR stock motor. I am the original owner and have always used 91 octane fuel. I have had a pinging/knocking noise coming from engine for the last 3-4 years. I have done several BG fuel injection services over that time and just this week did a BG GDI fuel service. The BG chemicals sat in the engine over night and then service was completed the next day, so the engine is de-carboned at this point. The pinging/knocking never seems to go away after these fuel services. The pinging/knocking only occurs between 1,500-2,000 RPM when the transmission is in drive with light-medium load and when the engine is at operating temperature. It never pings/knocks when the engine is cold, in neutral, or park when revved to 1,500-2,000 RPM. Since the engine has been de-carboned, are there any other possibilities that could be contributing to the pinging/knocking? Please help! Thanks