Dean Ing's stoppage-time strike sealed Gate's sixth win in seven unbeaten games under manager Andy Clarkson and saw them climb into the top 10 of the Hallmark Security League premier division.
But they had to come from behind to beat and Irlam side who also arrived at the Brian Addison Stadium in form after a good win over West Didsbury.
Gate recalled Ing in midfield in place of the injured Andrew Richards but it was Irlam who started the brighter and had the better of the first half.
They couldn't capitalise on a series of set-pieces until a minute before half-time, when the unmarked Connor Martin headed home a floated cross at the back-post.
Clarkson clearly had some choice words at half-time as a completely different Gate team came out in the second half.
Even so, it needed a superb, full-stretch save from Ben Fletcher to deny Irlam a second on 62 minutes.
Gate equalised with a superb free-kick from Gary Pett on 72 minutes, the sweetest of strikes from just outside the box.
And the hosts went on to seal victory from another free-kick in the first minute of stoppage time, Ing powering a header home at the back-post.
Gate saw out the final few moments and now look forward to Saturday's trip to Barnoldswick Town.
Gate: Fletcher, Colquhoun, Higham, Masters, Carroll, Pett, Hall, Ing, Moxon, Williams, Buchan. Subs: Cornwell, Moorhead, Cech, Charnley, Atack.