I have been chasing a low heat problem on my old Kenmore gas drier. I first ordered and replaced the gas coils and while there the flame detector and the igniter. The flame went from being on 3 seconds to 10 seconds every minute. I then replaced the operating thermostat and the flame stayed on 15 seconds per minute which reduced the dry time for a wet load.
The repair guide advises you to ohm the parts but I suggest replace them all if you have no history of being done. You see, the flame time will depend on several sensor readouts. If they are marginally ok they will show acceptable when you ohm them but the compound tolerances may barely enable the flame for a couple of seconds. (Electrical components that slowly die with reduced performance).
Be sure to watch all the videos related to your problem and take notes of the parts needed. Appliance Parts Pros had my parts delivered quickly hassle-free even in these shutdown times. Stay safe everybody