think i found it... page 182 Continuous Low Mode Shooting Speed. you can do 1, 2, 3 or 4 fps. the default is 3fps. haven't tested it out yet. hopefully there's no imposed limit other than battery life.
No, that's a different feature. The faster pro dSLRs had Ch and Cl in the mode wheel and Ch was the max frame rate and Cl was user selectible from 1 to 1 under the max. When the D80 was 3fps, that wasn't needed, but the 5fps D200 had it as did all of the other 5+ fps cameras. Now the D90 is 4.5 so they decided to include it. This has nothing to do with the intervalometer.