We were thinking something along those lines also, but for the amount of material and where it ended up it just doesn't make sense.
The throttle body looks great, no issues there. I know the broken valve spring on the exhaust side is definatly causing most of the rough running but we can't figure out what the loud knocking noise was. It's really strange. We just want to make sure the new engine we install doesn't end up like this one. I really feel something devious happened. I will post a picture of the material we found.
