Now it's time to play one of our favorite games around these parts: What The Hell Is This? Our subject is the 2015 Ford Mustang, specifically what seems to be a high-performance variant seen testing in Dearborn. The catch is that it doesn't sound like it has a V8, so what the hell is it?

The video comes to us from our pals at the Mustang6G forums, where they point out that the car seen testing appears to be similar to the Mustang GT350 prototype that's been running around lately.

There's one notable difference: the quad-exhaust is gone, and the exhaust note is entirely different. They aren't sure it's a V8, and it doesn't sound like one to me either.

Here's a video comparing the prototypes. Hear how different they are?

Maybe it's some kind of high-powered EcoBoost turbo four Mustang. Since the Mustang EcoBoost is getting all the nice equipment and performance packages, it could follow it's getting its own beefed up version. Perhaps it's the SVO we all want.

But to me, the exhaust sounds raspier, like it might be a V6. Maybe it's a V6 performance special? Or an EcoBoost turbo V6 tester? It's awfully hard to tell here.

Your turn, Jalops. What the hell do we think this is? Does anyone have solid clues what its deal is, and has anyone seen this running around the Detroit area?