Engine noise Vauxhall Astra 1.6

[alan1990]

Hi

I have a Vauxhall Astra 1.6 13 reg last, week the car started making a noise to that of a blown exhaust but only makes this noise when the car is in gear and driving mainly in 1st 2nd or 3rd while accelerating.

It does not make it when the car is in neutral.

Car drives as it should and changes gear fine.

Any ideas on what it could be?

[mfmman]

Are there flexible joints in the exhaust manifold, could be opening up a split as the engine moves under load