well, when you first start it up after a couple hours it will shake real bad then once it warms up it will still shake but not near as bad. my boss thinks its the year old gas making it run rough. Although when i hook it up to live data on the snap on scanner it only shows a misfire a couple times a minute for just a split second. Anybody have any input? I've replaced the plug wires, plugs, and coil pack.