[Engine power is reduced]

Thank you for your help ill give it a go

[Engine power is reduced]

I have just become the owner of a Vauxhall Astra 1.6 Diesel CDTI SRI 65 plate and every now and again i get a warning come up on the dash thats say “Engine Power Is Reduced” and the engine does lag a little as if its missing a beat and then comes back. Any advice?