Steering wheel follows road surface imperfection!

[Sardine]

I don't know how to diagnose this condition. My 2004 V70 FWD 2.5T 100K km has developed a tendency to pull left or right according to the road surface imperfections. It is not a major problem as the car is still very drivable. The tires haven't been changed, lower control arm ball joint seems OK, tie rod seems OK. Installation of the IPD bushing inserts did not help. Is there any test I can do to determine what's going on? I'm thinking of replacing the lower control arm since I don't know what else to do. Is it possible that it is a steering rack problem?
Help please.

[nsjames]

seems ok when checked how?

you need a good sized prybar to exert enough force to inspect them. if you just grabbed the arm and tried to move it by hand you're no where near the amount of force needed.
Check with prybar between arm and subframe, I'll bet you find the LCA bushings are wasted. That will cause changes in your toe depending on road surface crown.
It is possible it's a rack problem, but more likely would just be tie rods. Racks usually fail with leaks, or crunchy noises when steering.

[oragex]

When tires wear some have this exact tendency. Same for me. My control arms are new, geometry checked, struts new, and it still 'tramlines'.

Or it might be the camber setting, I have a negative camber.

[Sardine]

Well, I had another try with 2 foot long prybar between the subframe and the arm like you said, the thing didn't budge at all on either side. I couldn't push the arm up due to the long prybar but I did exerted pretty good downward force on the arm. This car has spent its entire life in city so I expect at 100K km all the bushings must still be OK. At a recent wheel alignment after the bushing insert installation, the mechanic said everything was perfect.
Where to go from here? I'm not sure but it could be the tires, like Oragex said.