It happens to me 2 years ago and brought it up to the dealership, they took out the cowl hood and clean inside it. They said it clogged with pine needles. So i think thats the same problem with your friend, i know you check the plug but check it again..
2016 GT RACE RED MANUAL aka " RAGING BULL"
Borla stypes cat back exhaust, tint kit all lights, 5.0 race red shift knob, MMD V SERIES SPOILER... and more to come...