Very Crispy Noise From My 2007 Galant. Suggestions Needed. Thanks! Options

[nemazch]

My 2007 Galant ES began to give some very crispy noise recently. I sort of feel sad, because it is only around 13500 miles. To me, it is like some vibration noise coming from some very thin metal sheet. It mainly happens when I step on the accelerator, or start the engine. After driving for a while, the noise seems to go away. As I don’t have a Mitsubishi dealer in town, I went to a small repair-shop to get some quick suggestions. A tech heard it for a second and told me it is due to some heat shield (rust, loose bolts, etc). So I want to get a second opinion, and went to another repair-shop. It was very funny (and unlucky for me) that on the way to the 2nd repair-shop, the noise is there, but after I got a nice tech into my car and drive around, it just would not give any noise! But this is not it. I then went to try the 3rd repair-shop. SAME thing happened to me (noise on the way, but no noise when the tech is in my car). I was really pissed, as of now, sure enough, the car is giving noise again. I hope some of you guys can give me some comments/suggestions. I simply want to get myself more prepared before heading to the dealer, which is about 60 miles away. Will this problem usually be covered by warranty? I am the original owner.

Thanks!

[nemazch]

Update (in case this can help someone):

The dealer fixed the problem caused by muffler heat shield. Tech said this is a common problem for 05, 06, and 07 Galant, and Mitsubishi has issued a technical bulletin. BTW, there was no charge for me.