Air purge valve starts leaking at 105 psi

Too many mechanics are simply parts changers. Anyone can throw $$$ away on parts. Something doesn’t add up . Good Luck, second opinion is needed, maybe

 

i have volvo automatic 2013. problem is truck slows before it purges. slows down like i am hitting the brake. like i am driving 65 mph when the air builds to 115 psi the truck slows to 60 mph it’s like the same as i hit the brake for 4 seconds after that i hear the purge. then the air gauge stars to drop slowly until 105 psi and truck starts to run normal. this happens every time in about 20 minutes i want to the volvo they can’t even figure out. any help i appreciate.