Running cylinder tests

[Lonestar10]

When doing cylinder cut out test today when trying to run on a single cylinder 1,2,3,6 all start out fine for about 5 seconds then it seems every compression stroke it loses about 50 rpm till truck dies. 4, 5 keep right on chugging.

Cylinder performance test shows 1,2,3 bouncing back and forth between fail,pass and 4,5,6 stay on pass.

Injectors were done in March with overhead
Actuators in december and fuel shutoff.
Fuel filters are new, rail pressure 270 at idle, 775 rpm idle

Any ideas? Don't have bubble test kit on hand as I left it at my mechanics for him to use as i thought i wouldn't need it for a while.