My MJ has been feeling a bit squirrelly going down the freeway at 70-80 MPH for quite awhile now. Not terribly bad, but worse than I liked it. Since the lift I had replaced every bushing or steering/suspension part up front (new WJ LCAs, new UCA bushings, new Teraflex adj. track bar, ball joints, new ZJ steering box, steering box linkage, etc.) and everything was tight with no play. My caster reading at the upper ball joint flats read +4 degrees on both sides, so I decided to add another caster shim behind the LCAs. All I could find were 1/8" thick shims, so I threw one in on each side. The caster measurement went up to +7.5 - 8.0 degrees, dead on. Took her out and what a difference - solid at speed and on bumpy roads too, no wander or steering play. It made a big difference. Dealers do not stock the shims anymore, but aftermarket 1/8" thick caster shims are available HERE.
TIP: Check your caster with an angle finder and correct it to as close to 7.5 degrees as you can. It's easy to do and it really helps the road manners. If your rig is 4WD, increasing the caster also increases your front drive shaft operating angle, not good. You'll need to experiment with the caster while watching the drive shaft angle, and drive shaft angle always has the priority. The Moog 1310 u-joints can handle up to an 11 degree operating angle with no problems.