LQ4's only have iron heads in 99-00. They do have less compression (half a point) and weaker (by high standards) rod bolts up until the mid-oughts as well dished pistons (whereas the compression on an LQ9 comes from flattops). I'm pretty sure the LQ9 came out in 2002 Escalades. Pretty much all LQ4's AND LQ9's 2003+ are DBW. Most "older than 2003" 6.0's of either type are the old style DBW if found in a utility (Denali or Escalade). The 2500 6.0 truck up to 2002 usually have DBC.