I was cursing along at about 45mph and out of no where I start hearing the engine makeing a very loud popping noise that was coming back through the intake, so i quickly pulled off and cut the engine. I have heard this noise before when i was replaceing my injector orings and didnt have a rocker arm tighten all the way. Also about two days ago I came out of the gym and noticed my fuel cap was off...... and I'm pretty sure I did not leave it that way. So all ive had time to do is take my fuel filter off and drain the fuel bowl. Of course theres deffinity something in there, fuel filter is coated in a brown greasy film and on the bottom of the fuel bowl there is more of the substance, covering the whole bottom atleats cm or two thick (brown on top and then silver on the bottom). The acual fuel had a blueish tint to it. Anyone know what this could be? And does it make sense that the substance could gum up a vavle and cause the popping back throught the intake?