For my stock 2WD XJ I really like the Bosch 7mm Opti-Core. They smoothed out a rough idle I had.
But if your rig has significant performance upgrades like intake & exhaust, you might want to look for 7.5mm - 8.5mm wires. Accell sells some huge 8.5mm wires. Wires with good core architecture will help electricity flow better, & Accell has a good rep. I should also mention that I've heard the Mopar "performance" wires (a step above standard or OEM, I guess) are great.