Pre facelift models have a history of steering rack problems - the rack is controlled by electric servo motors and when faulty can cause the steering to feel "sticky"
On later models they went back to an old fashioned hydraulic system.
The pre-facelift cars' "sticky steering" issue has nothing to do with the steering rack or servo motors - it's due to a malfunction of the ECU on the steering column when subjected to high temperatures.
This can eventually get so bad as to necessitate an upgrade to the post-facelift ECU - unfortunately attached to the steering column for good measure. Yes, the whole lot has to be replaced (around 2.5k repair !)
The good news is that your problem does't sound like "sticky steering" to me (I've experienced this on mine so I know what it's like) :wink: