there is no issue with pump, no tuning is needed @ 1 lac kms. if your car is giving u good diesel average and pulls good on hilly areas i mean no power loss then your pump is in tip top condition, its just lack of knowledge about diesel cars in people's mind. little black smoke under sudden or heavy acceleration is normal. is timing belt changed? and dont drive on low fuel level, fill ur car up only from one reputed station in ur city.