Fuel Pressure Drop at 3k only?

[355chev]

Hey guys,

Haven't posted in a while. Here is the problem. My fuel pressure stays steady at 28-29 psi. Under WOT from dead stop stays at 28psi, then at 3k rpm it drops off down to 15 psi, truck falls on its face then in a half a second time it comes back alive, fuel pressure goes back up to 28psi. This is on a full tank of gas. What I found out though it only does the fuel pressure drop from a dead stop WOT. When you're rolling along at 5 mph or so and up, then stomp it its fine doesn't fall on it face at 3k. I hooked fuel pressure gauge up and routed it to right in front of windshield to I could watch it drop so its not tuning problems in my opinion. Any help would be much appreciated!
Here is a video, its hard to see gauge but you can hear it happen and watch needle go up and down.

Thanks
Max