Squeak in the front left
 

I need ideas for what could explain (and what to do about) a high-pitched squeaky noise in the front left. Happens when I bring the steering wheel back to center after turning to the left. Noticed it first time about 6 months ago; was very intermittent at first, mostly audible in the morning as I started driving the car, then it disappeared during the day. Now it seems to get worse, I can hear it almost every time I drive the car.

Does not happen when I first turn the wheel to the right, then bring it back to the center.

The car is a 2007 997 C4S with 40,000 miles, used as a DD. Bought it one year ago with 27k miles from local dealer. Took it to them about 3 months ago, they "heard nothing" ( I have a full warranty through them, maybe that acts as a disincentive to find stuff). But they said something about a crack in suspension mount but apparently "did not need attention".

Any suggestions are much appreciated.