i have a 04.5 duramax that is stock.it has 36000 miles on it,and it has a raw fuel smell that will burn your eyes. i scanned the computer,and there are no codes, or service lights on.it has a spark knock sound that sounds like a gasser with low octane.i checked the injector balances at idle and they are .00 to .03. the only thing i notice is that the egr valve always read that it was open, at idle and if you rev it up.any ideas? i just bought from a dealer and its a certified used truck and under warranty for 3 months and 3000 miles, and i want to have an idea what may be wrong before i take it back.

Has a blocker plate been installed in the EGR tube? I noticed more fuel smell when I blocked mine.

Is the knock there when it is cold or after it warms up? what RPM is the knock sound present at? Do you have any mods installed?

The knock is there cold or warmed up.Its at 1800 to 2000 rpm with light throttle pressure.It doesn't do it at idle or when you accelerate. The truck is totally stock right down to the 245/75/16 10 plys.