If you have a problem with the high pressure pump it may be that the pump is "breaking up" internally, which causes swarf and iron filings to get into the fuel system. This in turn can cause damage to your injectors and can be expensive if not dealt with quickly. You may want to check for "blow-by" which occurs when the injector does not seal against the injector seat in the cylinder head. Often a "chuffing sound" is heard or black "tar" can be seen around the injectors. Sometimes this can be rectified by removing the injectors, cleaning them and renewing the copper washer. In serious cases, it will require the seat to be refaced.