Well, after installing on 2 different 5.3 GM products, I can say the noise is consistent. I can wrap rubber/foam around the PCV side hose and dumb down the noise considerably, but I've opted to return it. I can't be ok with a $150 separator that is this noisy and needs better sound control. I suspect it's a combination of the "can" and "filter" together with a restricted diameter vacuum hose creating a resonation chamber. It's pronounced. You can hear it with the hood closed, sitting inside the truck. Not going to work for me. I'm sure the unit works as advertised, but I just can't be OK with that noise. One other thing to note: The hoses are very soft, especially after sucking hot air from the crankcase. I could see these hoses at least partially collapsing after many heat soak cycles. Something to keep an eye on. Will update on how their return process goes. Reading their fine print, sounds like I'm going to take a re-stocking fee hit and lose return shipping. Still better than listening to SUCK SUCK SUCK while the engine is idling.