Awful Crackling Sound

[unh1569]

Hello,

First time poster here. I have an 04 g35 6mt sedan. 85k miles. When I accelerate in any particular gear and then let off the pedal (without shifting)I am geting this bad crackling sound. I cant tell if it is coming from the engine or exhaust. The cars performance does not seem to be effected. I have had 2 mechanics look at it and neither could figure it out. One thought it was coming from the exhaust. Has anyone had this problem?

I am also getting the pinging noise at low rpm when in 2nd and 3rd gear...that seems to be a fuel issue though?