Vauxhall Zafira running problem?

Hi everyone, I have a 58 reg zafira 1.9 diesel. last week my alternator pulley broke and chewed up the fanbelt. I have had a new alternator, timing belt and fanbelt fitted but ever since my car has been very hard to start. So I changed the glow plugs, serviced the vehicle and replaced the starter motor. Now the spanner light is always on and still the zafira is hard to start and when it does start it is juddering and the whole dashboard vibrates when I press the accelerator. I am at my wits end and my mechanic is now saying that it may be the manifold air pressure sensor. When attached to the computer there are no fault codes. Can anyone help me out please.