does the idle surge when the a/c is on ( a/c is on in the two a/c positions and in the defrost and mix modes)
if it only does it in those modes then a low freeon charge can cause this. what happens is the a/c system short cycles and the pcm can not react fast enough to adjust the idle.
also make sure, ur not misfiring on any cylinders.. My idle was jumpin around as well, then i found out my 2nd cylinder was misfiring, and i fixed it, now the idle doest move.