Fuel Pressure Issue
 

A friend of mine has a 2008 SS manual with a few mods thrown on. He's been having a misfire/unsteady idle problem. The video is the best way to understand the low side fuel pressure. What's causing such a weird erratic fuel pressure?

A failing intank fuel pump. Corrosion in the fuel lines and or dirty fuel injectors. Just to confirm what air filter is he running? It could be time for a new one.

Fuel pressure stays extremely steady after shutting off, so I don't think there's a leak, and the sound in the video does seem to correlate with how the fuel pressure act though.

The video wasn’t that easy to see, but if that needle is bouncing the fuel pump is toast.

Yeah it was just moving too fast for the camera to catch it! Do you mean the in tank or the mechanical pump?

Edit: Nvm you meant in-tank pump

Could be either. That noise would lean me toward the mechanical.

I get "can't open file"

Doesn't matter Randy. Bad video. Can't see the needle on the gauge and the sound doesn't tell you much.
Here's a frame shot from the video.
https://cimg1.ibsrv.net/gimg/www.che...0b8971f3c8.png

As I understand it the High pressure is variable. I would check the low pressure pump by running it with the engine off bypass the relay because it will only run for a few seconds.