[Spoooky]

Tin-man, This happened to me and you said it was when you put on the brakes. You could feel a pop at the seat. There were a series of Superformance car #'s that didn't have lock tight or the front calipers nuts and bolts. You car # is right there like mine. Check those caliper nuts and bolts first. I had one sheer right off and lucky it was a a low speed not to do any damage. Contact Lance he knows the car #'s effected. It's worth a look for some piece on mind at least.