My 04 LB7 w/102,000mi has been smoking a little at idle. Well over the past week and a half it started getting worse.
Took it to the dealer today to get it checked out. Got a phone call this afternoon that 4-injectors are bad and all the injectors are being replaced on GM's dime. I am so glad this is covered because my warranty is out the end of October.
Thanks to everyone on this forum for all the info. I really appreciate it.

Congrats man. It can't get much closer than that.