Ok so my car has been making this funky noise for about 2 weeks, i first noticed it when it got pretty cold here (20*) and it has persisted since. I took the car to the mechanic today and he told me it sounded like a heatshield rattle. But it doesnt sound like a rattle, it sounds like something is failing. Its more of a grinding/scraping noise. And it only happens when the car is moving, at all RPM's not just the usual around 3k for heatshield rattles. The noise is most noticeable at the low RPM's because the engine and exhaust arent as loud. Any ideas???