Ayuh,...... Welcome Aboard Jan,....... Ok, so you have a 2001 kamd 44, which I believe is a Volvo diesel motor, 'n the turbocharger isn't working right,..??
The compressor, is it engine mounted,..?? is it necessary to help the turbocharger,..??
Obviously I don't know alot about your motor, but I do know abit about diesels, 'n never knew one that needs compressed air to work,....
Have the motor's fuel filters been changed, since this problem started,..??