Is the vaccuum control valve on the injector pump a regular replacement item ?
Can a defective unit be a source of many strange symptoms such as rough shifting and sluggish acceleration ?
It looks like a white plastic piece that could get clogged or weaken over time after high heat and vibration.

Is the EGR valve common to all diesels or was this intalled in only certain models ?
Wondering if this should be replaced or serviced periodically.

Thanks.