Just picked up a 98 TJ for the girlfriend to use as a DD. It came with a 4 inch Superlift on it and 33x12.50x15 tires. The guy I bought it from said the steering got sloppy when the lift and tires were installed, he put two new stabilizers on it and said that helped but it's still not great, too much bump steer. Just wondering where I should start looking to try and improve things. First thing I'm going to do is put on a set of 31x10.50x15's that I have just to see if that helps, but of course we'd like to run the 33's. It looks as if the lift kit used the stock link arms, but with 4 inches of lift I didn't think that would be a problem, however this is my first experience with coil spring suspension so I really don't know. Does 4inches of lift mess up the castor on a 4 link?
It's only got 56k on it, though he said the lift kit's been on since about 20k. Tie rods etc. don't seem loose, but I'm guessing it wouldn't take much slop with the bigger tires to mess things up. Any other ideas where to look?

If all control arms are stock then the castor is probably off. I would start by getting adjustable control arms to correct your castor problems..but you also need to get rid of the inverted-Y steering, this setup does not work well on lifted suspensions. You need to look for an inverted-T or crossover steering setup. Dual steering stabilizers are completely rediculous on a TJ on 31's (or anything for that matter), that is doing nothing but masking the problem at hand

I'm trying to visualize how the lift will throw off castor. When lifted, the lower control links will try to pull the bottom of the axle back, rotating the pinion up, but the upper links will try to pull the top of the axle back, rotating the pinion down. Dont' these actions cancel each other out, keeping castor constant while pulling the whole axle back?