[Jeff Williams]

David,
I also have a P-8. The pop-off doesn't make an unusual amount of noise. The apparently loud pop-off noise on the video may be due to the video recording device being more sensitive to high frequencies, rather than low frequencies. The sound of the wheels rolling on the track is much more pronouced than the pop-off sound on my track with the P-8 pulling a string of cars.
Jeff

 

[Jeff Williams]

Michael,
Since a picture is worth 1000 words, I'll first try by attaching three photos.

I hope this helps

 

[Jeff Williams]

Michael,
You are very welcome.
As to your noisy pop-off, I suggest that when your boiler is up to pop-off pressure, that you hold the pop-off closed (with a flat-bladed screwdriver or other tool) and let the pressure rise until the second pop-off releases, (hopefully only 5-10 psi higher pressure) to find out if the higher-pressure pop-off also makes the same loud noise. If it is not as noisy, then there may be something like a macining burr inside the lower-pressure pop-off that is causing the loud noise. You could then consider ordering a replacement for the lower-pressure pop-off from Accucraft. This test will also give you confidence that the higher-pressure pop-off is actually working!
Jeff