Signature 600 chuffing

[Creek]

No I’m not sure it’s turbo chuff, just sounds like back pressure being force out of air intake. I can faintly hear it on downgrades without using the engine brakes. On hard pull it pegs the the gauge at 35.. CAC was new about a year ago. It started doing this on a 80k load of wheat out of Montana in January. As far as I can tell it is factory turbo that came with the recon engine that previous owner installed.
Thanks for the reply.