People do still use this site to help diagnose faults / problems with their cars. It's up to the owner / OP whether they take the advice as the community here can't actually 'fix' the car for them.

Sometimes you'll get conflicting advice, sometimes you'll get incorrect advice but for the majority of the time, you'll get helpful advice. Obviously, if you have a problem, sometimes it's best to get your car booked into a trusted garage for diagnosis and repair, especially in the case of engine warning lights or the car going into limp home mode.

i have 2001 2.0 hdi pug 406 110

it have been on a computer and come with high pressure regulater jammed can any one tell me if i need a new pump or just the regulater it has the anti pollution on dash and in limp mode it also runs on for 3 seconds after turning key off

I have had several problems with a C5 using the same engine and all of mine have been due to the pressure regulator on the HP pump. It has a very fine stainless steel filter on it which clogs, you can just try grinding the end of the filter off as some don't have it anyway but make sure you get all the swarf out.

The regulator screws onto the pump with two torx or allen screws, you may have to remove the fuel filter but its not a difficult job.