Coffey was a known liar, I would not go by his version of things.
Can you givean example of him lying? He's always seemed pretty straight up and matter of fact to me.
I also don't know why he would lie about NOT putting the cigar in his mouth? If anything he would want to accept that to get credit for it. It's very plausible for Galante to have died with it in his mouth, I'm convinced the masked gunmen were more of a ploy to take attention away from the bodyguards. I think the bodyguards had a cue to take Galante out as soon as the gunmen entered, Bonventre probably blasted him while he was lighting the cigar because the lighter was still in his hand.