My Maytag gas dryer will not stay lit. The flame comes on for 30 seconds to a minute and then goes out. The Dryer keeps running and after a few minutes it lites again but goes out again and keeps doing the same thing.

I have replace the gas valve coils and all the thermostats, hi temp switches and the flame sensor as well as the igniter in the entire dryer. over $150 in parts and nothing has changed. Also cleaned every bit of lint and debris from the lint filter all the way to the exhaust opening on the outside of the house.

What else could it be?