Had noticed this last while that the astra had lost alot of power but though it was down to age and high miles (its a 2000 1.7DTI with over 111,000 miles!!) Was finially p**sed off with it when I couldn't pull away from a 1.1 pug!!!
went to the local vauxhall garage who couldn't have been more helpful, turned out it was the air flow sensor was faulty.
The difference it has made is unbelieveable!! Totaly feels like a new car!!!
The only down side is they told me that fittin an aftermarket air-filter was properly the cause of the problem, did anyone else have any problems after fitting an air-filter or is it a one off??