So, I bought an '05 salvage-rebuild tC a couple of months ago and have been loving it thus far. However, a couple of weeks ago, I heard a strange sound while making a hard left turn, and have heard the same sound several times since then (always while making turns), making me worried about wtf is going on.

For lack of a better description, it sounds like a hollow PVC is sliding and then whacking into something under the dash directly in front of the steering wheel (sort of a hollow "bonk" sound, if you will). I popped the hood and nothing seemed loose. Google searches haven't turned up anything, though I'm not really sure what terms I should search with anyways. No warning lights have come on and the car seems to be running smoothly otherwise (maybe a slight pulse in the brakes, but I doubt that's related).

Any idea what could be causing this? Even wild speculation would be appreciated, at minimum for its entertainment value...