Buzz at 4,000 rpm, 200RS

Experiencing a reasonably loud buzz from the engine bay once I hit around 4,500 rpm all the way up to the red line. Renault main dealer replaced the entire manifold (at no cost to me) and associated flexi hoses before they would let me take the car away (recently purchased in June) due to a crack in the original flexihose, my first reaction is that it is something to do with the fitting of the new manifold. I know the cold air induction kit on a defender I used to run buzzed like crazy under heavy acceleration so my other though was a potential induction issue?

Any advice would be much appreciated.