what all can purge do to a car?
 

what all can purge do to a car? can it increase vacuum from the pump?

For my 85 300D it didn't really do anything. But for my mom's old 300SDL with the 603 it made it start waaaay easier... like as easy as a 617 starts.. and no smoking @ cold idle. But it was temporary, lasted a couple months before starting to do it again.

No it won't do anything for your vac pump.

Hear Now! You need to rid yourself of that "gasser" thinking.:D

Diesel Purge is strictly for the fuel system.

Some things to consider:
Ensure there is no algae in the fuel system (in-line, see-through filter is not black and remains clear for period of time)
Have new primary and secondary filters on-hand.
Do valve adjustment and run for at least 200 miles before determining usage of purge. (It is not a cure-all.)