Sorry to butt in the thread but my car with stage 1 revo has all of a sudden started doing this through the rev's. I am servicing it tonight with a couple of mates and changing the spark plugs and coil packs just incase...
Have had revo with 7 - 5 - 9 setting for a while and no issues at all... then all of a sudden BAM! cough cough cough as she revs.