As the title really. Over the last few weeks the car seems to have developed a real kick to the steering when you apply power or come off the power. It hasn't done this previously so I'm pretty confident it's not standard diff behaviour. Besides, it does it when you're well within the grip limits on a pretty flat road, (e.g. 4th gear at 50mph, apply about half throttle and it kicks 10deg one way, come off the throttle and it kicks 10deg back the other way). Alignment was done pretty recently and the tyres have plenty of tread with good consistent pressures. Am I looking at a swivel bearing? This normally seems to have grinding / noise on the steering at full lock but I don't seem to have any of this. I do have a whine coming from the gearbox but that's not getting worse and has survived through two trackdays now.