Yes, stock configuration is simplest and most reliable.
You can find jets for pre-gen Ninja here:
http://jetsrus.com/a_jet_kit_street/...1988-2007.html
To free up stuck jets, i usually use an ammonia solution (floor cleaner) to dissolve corrosion. Then PB-Blaster. A light tap with hammer-driven impact-screwdriver really works well and prevents stripping jet. Not sure why these are made from soft brass, seems like copper-beryllium would be better.