
Chances are a steering tie rod end, steering knuckle ball joint, control arm bushing is knackered. I've had death wobble once and it was a steering TRE, the only other time I've seen it was also a steering TRE.
Just fitting 4.5" springs and shocks is the start of getting the jeep working right at that height. I would suggest you need to look at rear prop angle (fit slip yoke eliminator), front steering angles and alignment (fit adjustable control arms & adjustable track bar and lowering bracket at body + dropped pitman arm) also things that may have come with the kit like extended brakelines and bumpstops.