Ok I've followed your advice an I'm now using sync2() copied into my code. I've added options for switching between sleep/yield and the perf/lwjgl timers so hopefully something will show up now. The graph does look different with the different combinations, but nothing noticeable in performance on my machine... the results look like this:
non-vysynced:
lwjgl/sleep: steady 2millis flux
lwjgl/yield: flat line
perf/yield: mostly flat, more spikes than others
perf/sleep: random looking 2millis flux
vsynced:
lwjgl/sleep: steady 2millis flux
lwjgl/yield: steady 2millis flux
perf/sleep: flat line
perf/yield: flat line
I certainly don't need a detailed report like this from anyone, but I would really like to know about combinations that stop jerking on computers that have the problem

1 will toggle the pause method (sleep/yield) and 2 will toggle the timer (lwjgl/perf).
Every once in a while the screen went blue while changing between timers... not sure why, but I'm not surprised since I'm changing timer resolutions in the middle of running a time based game... It doesn't freeze the system or anything, you can exit normally.