There seems a general misunderstanding about how those gas sensors really work: the "heater" must be switched on (5v) and "off"(1.4v) for the air sample going in and out of the sensor, when heating the air sample expands and goes out of the sensor, then in the cool down period the remaining air contracts and sucks in a new sample.
Those boards with mq... sensors only provide fixed 5v heating, so this can never work reliable
the 1.4v is needed to keep the sensor on a minimum temperature,example 40'c for the catalyst to react, the 5v will heat it up to example 80'c, to clean the catalyst and air flows out of the sensor
http://i49.tinypic.com/2rzdqgn.png something like this will work
Soon I will report my results together with a modified sketch for mysensors 2.0