Interesting comments in another thread about a minimum nozzle size vs. pump head. Too small a nozzle & the resulting back pressure could lead to issues...
Sounds like this is just what I was looking for. A link maybe? I did a search for "minimum nozzle size vs. pump head" and nothing came out - but this one.
Note: inj.refs 520 seem to correspond to different sizes whether they came from Bosch or Bosio (eg: Power+) ...
It was a comment about a 11mm head from a auto & the stock 5spd tdi nozzles. I wouldn't think that would be a huge problem but going to a 12mm unit & having too small nozzles could lead to issues. With larger nozzles you can always reduce the fuel manually to avoid smoke.
5 speed nozzles are bigger then the auto ones though.
Ooops, thanks Tyler, I meant it the other way around...