I have a 2007 truck and a 6.0L with a hissing sound. The truck has about 182k miles on it. I’ve checked the CAC tubes for cracks, put my ear up to all the boots and the hissing muffled itself which leads me to believe it’s not them. It sounds like it’s somewhere about the turbo area, I’ve checked the turbo/Y-pipe connection with bubbles while the engine was running and after I turned it off. No visible bubbles were forming. The truck has been bulletproofed, straight piped, deleted and tuned. The hissing noise is very prominent when it’s cold and just being started. It’s also loud when I’m accelerating. I can’t hear it in the cab but I can smell exhaust while sitting in the cab with the windows up and everything. When my windows are down and I take my foot off the gas I can’t hear it, but when I put it back on it is louder than my engine’s sound (besides the exhaust itself). I’ve sprayed down the turbo, CAC tubes and the turbo intake clamp with soapy water and nothing. I don’t know if an intake leak would make a leaky air compressor tank sound like it’s making, but it might. It’s very annoying and I would like to solve the problem. I hope it’s not the Y pipe in any other place. I’ve looked around online but came up dry on my symptoms. Some people have related but not exact. I can hear the hissing on the driver side, passenger side, and in the driver side fender well (lifted truck so I can get in there). It sounds like it’s under pressure or being sucked in or pushed out more while under acceleration, it doesn’t whistle just sounds like an air compressor with a loose fitting. Builds boost fine 25 pounds on moderate acceleration. I can work on engines and make them run right but this has stumped me, I’ve checked everything that I would think was wrong. I might need to look at the intake boots and connections but I’ve never seen those make an air escaping sound