Truck vibrating sometimes when jakes are on

[Magard]

Does your jakes feel like they work good. What boost do you see. I just had a new ecm put on my truck because the jakes weren’t working right. Only half the engine would Jake. On 3 the jakes worked surprisingly well. Seemed a little ruff but hard to tell until you got down to about 1300 rpm. Then vibrated. That’s 3 cylinders Jakeing awful hard with the vg running tight on the third setting. The tell tell sign is under jakeing switch the jakes between 1 and 2. You should be able to hear the sound change. Mine had no change. It had a code for jakes but no cel. Just st thought maybe that would help some.