GMFS Military Member
not sure when this started really but its been happening more often. When I accelerate half throttle or cruise at part throttle etc, there is a hissing sound that happens from under the hood. If I floor it or let off the gas it stops. Only happens at partial throttle. Im pretty sure its not an intake leak. Im wondering what else it could be. When its in park and I rev it , it wont make the noise so Im a little stumped. Belt? Exhaust leak? anything im missing?