I have an 04 Sierra slt crew cab Z71 with the 5.3.. I just bought it about 2 months ago.. Not long after I noticed a small puff of blueish smoke after I cranked it.. And then I noticed it was using oil.. I've read a couple threads and talked to some friends and come up with either the pcv or valve stem seals.. but then someone said the pcv in my model cannot be replaced.. So I'm just left scratching my head..??