I got same kind of problem
My america is a 2009 EFI I bought on september 2009.
2 Months ago my vendor detected a noise inside the engine (I didn't hear anything).
He disassemled the engine twice because, the first time, He had not solved the problem.
The second time he disassembled the engine, he found that a piece witch it supposed to be an "anti noise" internal system, was not tighted well and did not make its function of "anti noise" system (a kind of silencer). I have no idea what he talk about
. The sound was like pieces of metal that clash themselves , he said.
I don't know if he replaced the piece or just tighted it well. All was under warrenty. I did not paid anything.
I returned 2 weeks after to my vendor by him to control if noise was still here. And It was'nt.
I don't know if that could helps you and if what I wrote is well understandable ...
