It's almost as if the engine has a loose rocker, exhaust leak or something of that nature. Listen closely at 0.07-0.10 seconds. Engine is recently rebuilt to a 383 stroker, cc305, stock heads and mid-pipe headers.
There are some other background noises I picked up so please disregard them. The best way I can explain it is a GUZZLING type noise. At 4th gear it hovers around 2k rpm and when you give it gas you hear more motor than exhaust and the rpm's don't increase. When you turn the motor off you can sometimes hear a rattle noise under the valve covers.
Automatic, egr and tune recently done as well.