My DS is colicky and he grunts when he's gassy. He's been like that since he was a couple of days old, I even remember asking my HV if its normal lol. When I think about it he's not grunting as much as he used to, he's 9 wo, but having said that I also realise that he grunts more at around 6 am. It really puzzles me as to why it's always at that time.