Bit of a long story. Whilst driving around 3 weeks ago our astra breaks suddenly became hard to push and engine management light came on amber. Got the AA out who confirmed pieces of the break vacuum pump had snapped off, this at the time was also preventing the car from starting. Bought a new vacuum pump and a mechanic had managed to get out all the broken pieces from the engine. However the car still struggled to start and when it did eventually start we took it for a drive and the car had no power and struggled to get up hills or pick up speed on a bypass. Engine management light came back on and a diagnostic test showed this was due to the cam shaft sensor. Had that changed and the car is still struggling to start and still no power and still showing an amber engine management light. We was told by a mechanic that the only other thing it could be is a stretched timing chain however when I've mentioned this to other people they don't seem to agree as the car drives fine with no misfiring or noises, only issues is the car struggles to start, engine management light is amber and car doesn't have much power.