If it is does have drive by wire, then it should be a 03+ motor. Also I don't think the 411 pcm will control the drive by wire.
My '02 Yukon had electronic throttle control (ETC)... often referred to as Drive-By-Wire. So does my father's '01 Yukon XL. This wasn't just an '03+ option.
*edit*
Guzzler... you're right about the "Z" engines. That's what was in my Yukon (before I sold it).