Volvo Repair: Engine cutting up, volvo 780 bertone, volvo problems

Question
Hello,
I have Volvo 780 Bertone (year 1989).
Last week the engine suddenly started to die intermittently while running.
I brought the car to a mechanic and he replaced the spark plugs and the oil pump and the relay but the engine still dies and the car seems to have less power than before.
The mechanic says that there is not too much information about similar Volvo problems.
Is that correct and if yes, where can I find any info on how to diagnose and correct this problem? I love that car and though it's pretty old (216K miles) I don't want to part with it yet.

Thanks in advance
Regards

Answer
Hi Ivan,
        Many things could be a problem.Fuel filter,fuel pump,Air Mass Meter,one of the control systems could also have a problem.
         You should have a mechanic with advanced knowledge assess your car.You could spend hundreds to fix it and never find the problem.
          If you love the car,take it to a Volvo service dept.Getting a good diagnosis is the only way to go.
                   Good luck,
                   Bilbo