First, is the rack leaking? How is the fluid level in the reservoir? Have you listened for mechanical noise? You should check for sloppiness where it bolts to the inner tie rods and lower steering shaft u-joint.

Also you might want to check the 2 steering shaft u-joints. Particularly the lower, which is the one that normally goes. The u-joint could be worn out - especially at 350k...:) If you're lucky it might only be binding up. Try spraying a lube at the joint as you go lock-to-lock with your steering for a few minutes. Soak it down and hit it from different angles. BTW - This might take a few tries but it's worth it since new OEM ones are close to $100, if they are still available... I know the upper u-joint is not.