We have a 2005-EX-L-RES. There is rattling coming from underneath the car. I only notice it when going in reverse in the morning and sometimes when idling. I looked under the car and I can see a big metal piece shaking. Is this the heat shield? If so, do I need to do anything about it? We are going on a long vacation in a few days, but I don't have alot of time. Thanks for any advice.