this has happened on 2 cars mine was one. I had a clank I would hear from the front suspension. it wasn't consistent on the track it would happen every 4 or 5 laps. it wasn't the steering rack it's the nut on the lower ball joint coming louse. if you don't catch it early it will ruin the hub support by making the hole oval. if the nut comes off the wheel will collapse and its all over 911 time. I nut and bolt my car after every track day and never checked the lower ball joints. if you jack up your car and grab the bottom of the wheel and push it back and forth there should be no play. even if there is no play still check all 8 ball joint nuts (19mm). both times its been on the drivers side . carl