Game-changer Gow - on as a half-time substitute - was fouled by United right-back Joe Oastler and got up to roof home the spot-kick.
Torquay took a 15th-minute lead through top scorer Rene Howe's deftly-converted penalty.
Howe wrong-footed City keeper Artur Krysiak with his right foot chipped spot-kick into the roof of the net.
The Torquay forward won the penalty after putting pressure on Kevin Amankwaah at the far post as he went to head Nathan Craig's deep cross from the right.
Howe appealed for handball and referee Craig Pawson awarded the spot-kick.
City had a good opportunity to reply when midfielder Steve Tully teed up substitute Jimmy Keohane, whose angled drive flew just past the post.
City boss Paul Tisdale introduced striker Gow to pep up his shot-shy attack at the start of the second half and he went close with a low drive from the right as Exeter sought a leveller.
At the other end, Krysiak had to be on his toes to tap over a Billy Bodin volley.
United keeper Michael Poke then went full stretch on the goal-line to keep out Keohane's cheeky back heel.
