Yeah you can Advance and/or Retard the Timing on the 6.9l and 7.3l IDI. Its a pretty simple deal, Theres three 9/16 nuts on the IP side of the IP gear cover, loosen the nuts a little and you can rotate the IP. I forget which way for Advance/Retard.. I have always set it while the trucks idleing and gone by sound and relation to the mark on the IP and Timing gear Cover