The rack mount bushings may be toast.
They live a hard life, and often get covered with power steering fluid/atf. This causes them to swell/deteriorate, and then the rack can move on the crossmember.
Have someone move the steering wheel back and forth, and watch the rack for movement on the crossmember.
Only one side is still available new from the dealer. Luckily, it's the one that centers the rack. The other bushing can be built up with a scosche of bicycle handle bar friction tape or whatever you have on hand.
If you do replace the centering bushing, it has a little nub on it that makes it really hard to install. If you would like a few tips on how to replace it p.m. me, or just ask, and I'll post a few tips I've found that make this job easier.
Replacing this bushing improves the steering feel, and makes the car much more stable at speed.