[SNS]Manager Martin O'Neill says Celtic's four-goal flurry in extra-time against St Mirren was like "vintage Celtic" and ought to give them a boost for the title run-in.Kelechi Iheanacho, twice, Luke McCowan, and Benjamin Nygren scored in the space of six minutes to see off St Mirren 6-2 and book a place in the Scottish Cup final.O'Neill's focus now turns to the final five games in the Premiership, as Celtic chase down Rangers and Hearts, starting at home to Falkirk on Saturday."Confidence should be high with the team, particularly after the four-goal salvo against St Mirren in the semi-final last week," O'Neill told Celtic TV ."That should give any team a major boost of confidence."It was a throwback, almost like vintage Celtic, and it was like throwing away the shackles and playing with confidence and going for it."Iheanacho's clinical finishes and James Forrest's impact off the bench will give the Celtic boss plenty to think about for the visit of John McGlynn's side, who have lost four times to the champions this season."James has made a big impact in coming on in games, and that is difficult because sometimes you don't even get to the pace of the game until it's too late, but he has made big inroads in matches recently," O'Neill added."James Forrest has been a really good player here and in one-v-ones, even at 34 years of age, he retains that little bit of zip."And there's been a new surge for Kelechi as well, almost challenging him to be the player that you know he has been, and he has got fantastic ability."