when driving at interstate speeds, my 03 XJ8 has a tendency to require more steering input than i'd like when there's a moderate cross wind. i'm
running the stock 03 XJ8 wheels, with new Firestone factory-spec sized tires.

the car had a complete 4-wheel alignment less than 10,000 miles ago.

i did put new KYB shocks on the front a couple of months ago, but am still runnng the original shocks on the rear... 70,000 miles.

is it possible that the rear shocks being a bit soft would allow for body
roll in the back, which would influence straight line steering? indeed
that's what it feels like from the driver's seat.

and no, i don't believe that i have issues with the steering assembly. it steers tight and runs on rails unless there's a crosswind.

 

In a word, YEP.

My X300 was doing just that, and also the rear shockers were on the soft side.

New KYB at the rear, and significantly different. Had the align checked, not done since owning the car (3 years ago), and the caster was a tad high on the RH side, and now it is sweet in all conditions.