60 series Detroit air box horn.

The Detroit dealer did not know what it was. After talking to some members it was a military upgrade and it pulls dust from the air box when running any boost. Just for smitts and giggles I thought I would find out how many psi the valve opened at. I took it off and hooked it to my house air compressor and used the regulator found it opens a 3 psi. I caped off the valve and took the truck for a ride but without some weight behind me I could only get 15 psi. The most I can get when the trailer is hooked up and climbing a good grade is 17psi. My horn weld was cracked real bad when I got the truck so I just removed it for now so I don't loose it on the road. I guess I could weld it back or just remove the whole system.
So with that small of a line coming off the valve / intake do you think there could be much of a boost loss? I don't feel like hooking up the trailer just to check and not many hills around here.