TNS went six points clear at the top of the Welsh Premier, but they did it the hard way as they overcame plucky Porthmadog with a goal deep into stoppage time.
A draw looked on the cards until John Lawless crossed, Nicky Ward hit the post and Marc Lloyd-Williams seized on the rebound for his second goal of the night.
Port could have few complaints on the balance of play, but Saints again failed to turn territorial possession into goals, or even decent chances.
After Chris Taylor had headed a good opening over the bar in the sixth minute, all TNS had to show for first-half domination was a handful of attempts on goal, none of which tested visiting keeper Ged McGuigan.
The visitors then rocked TNS by taking the lead 10 minutes after the break, Gareth Parry punishing slack marking at a corner with a near-post header.
Chris King replied by heading over the bar before Carl Owen missed a great chance to settle the contest, firing across the face of goal after finding space down the right.
The introduction of Nicky Ward gave TNS more threat upfront and Saints finally found an equaliser with 10 minutes left.
Scott Ruscoe got to the byline and crossed for Lloyd-Williams to head in at the back post.
Ward then hit the post, keeper McGuigan produced a superb one-handed save to keep out Ruscoe's goal bound 20-yarder and it looked as though Port would hold out.
But in a desperate final rally, Jiws grabbed the winner and was denied a hat-trick only by another good stop from McGuigan and referee Phil Southall's full-time whistle.

TNS v Porthmadog match report, photos and stats