I have had steering wandering issues and my 2002 F250 4x4 crew cab since I bought it a year ago as you have to constantly correct the steering.
My unit is all stock except for the super chip programmer I use for towing and it has 150,000 miles on it.
I thought that maybe it was the tires so I replaced them but the problem remained plus I replaced the stabilizer shock but same results.
Everything is tight and aligned.
I also tried the Lucas rack and pinion lube to see if that would help and I got minimal results.
I read somewhere in the forum that it was suggested the fix was to adjust the steering box 1/4turn CW which sits right on top and is easy to get too.
The procedure was to remove the lock nut slightly, use a Allen wrench and
turn it 1/4 turn CW and re tighten the lock nut and see how it feels.
Note: Put the wrench on it first, then put the Allen wrench in and monitor its position as it may turn on it own when you turn the wrench, just keep track of where it was when you started.
I did that 4 times at 1/4 CW at a time and now it feels great!
Whoever gave that advice was right on target and I thank You!
UPDATE: Now I have added a new Rancho stabilizer shock (not the OEM equal but the bigger version) and that really helped, I tried a new OEM version but it didn't do anything, Note: you need to buy THEIR bracket as the OEM bracket needs to be moved about 3inches toward the center to fit the new BIGGER shock, they want $60 for that bracket though
You can make the OEM bracket work but it takes a lot of work to fit.