Ford Mustang Heat Shield

I Have A 1999 Ford Mustang V6 I Hear A Sound That Sounds As If A Heat Shield Was Loose On The Car But Its Not My Heat Shield When I Put The...

The Car Is A Ford Mustang, Stick Shift, Has 240 000 On It, No Leaks I've Noticed ....but When I Left The Car Idle One Day For About 2-3 Min...