1993 7.3 IDI Turbo ZF5 Gear Clatter

What the heck is causing the gear rattle?
- 2 year old DMF/clutch
- 2 year old injection pump
- Brand New injectors 20 minutes before this video
Nothing changed after the injectors. I thought I just got a bad one or two a couple years ago. I got so fed up with trying to figure out which one was the culprit, that I just replaced them all. Nothing changed.
Any ideas out there? A bad IP, maybe?? Got it from R&D IDI Performance. I figure that if there was a bad valve or low compression it would smoke or something, but there's no smoke, even when putting the pedal down hard.