I am currently using a 5-door Peugeot 307 model '03. I know Pugs tend to engine break when you release the gas pedal but there is distinct high pitch sound that is produced. I do not like it. What is it? It sounds like metal-to-metal contact

Hard to say. Could it be a turbo whine? I would take the car to a repair shop and ask them if this is a normal sound for the car. If it sounds like metal to metal, then I doubt if it is . good luck.

Sounds like a fan belt shreaking with one of the fan belt components......more likely with the alternator. Check the condition of your fan belts and then the tension.