'90 5-speed "lurching" under low to half throttle???

Wasn't sure whether this was a post for mod tech or OEM so I'm posting here, seeing that it's pretty built.

Rig is: '90XJ 5-speed AX-15/NP231 with advance adapters HD sye. Tom woods custom shafts, Dana 44 with Nitro gears (4.88:1) and an OX locker, on 35's.

Here's the issue.
In mostly second, third, and fourth gears when I'm not on the power very hard it's "lurching" it's not the typical manual transmission slack from changing the throttle position. It does it moving up-hill also. It feels similar to the typical slack, but it's happening under circumstances where the typical slack could never occur.

Looking for ideas on what it could be. Transmission? Axle gears worn funny? A bearing somewhere?

It is kind of a random stutter/misfire feeling? I had the same issue and it was the coil starting to go bad.

no, not at all actually. engine is still very strong. it feels like it's somewhere else in the drivetrain. Like it's got a tight spot or something. It's pretty smooth and very steady. Not random.