Check the torque specs on all the suspension parts, especially the spring mounts and shackles. Alot of people have a tendency to over tighten when installing a lift. Try loosening everything and torque to proper specs.
Ero sum: aut viam inveniam aut faciam = I will either find a way or make one
Offroading is suppose to be bumpy lol..... JK .. x3 on checking the torgue specs... my step dad put 4in lift springs on his 95 wrangler and when you would hit any bump you'd basically be airborn.. we lossened them and it made a difference.. Still bumpy but not as bad.. but we also did the leaf over axle.