I think this might help you decide whether to buy new or clean.
It's a great video, pretty much all you need to know...
PorscheDude, your questions answered perfectly here as well.
https://www.youtube.com/watch?v=YZ4Zx6SPlMU
Bosch K-Jetronic Performance: Why Change Fuel Injectors?
Mercedessource
I just finished watching it.
Phil