Was mowing tall grass on a 90 degree day, with throttle nearly open, and afterwards noticed that this 26 hp intek started belching frequently. It doesn't exactly sound like a back fire, but on that order. It starts and mows fine, and when running at slow speeds, or idle, it is not as noticeable. I had just been bragging about this engine, which has over 1000 hours on it. It has been well maintained, uses no oil, and has always run perfectly. I will do some checking tomorrow, but wondered if others had experience this.