I suspect water in the gas tank of my '02 Supercrew 5.4 4x4 with 172K miles. It has developed an intermittent low-RPM miss in a steady slow pull (about 1500-1700 RPM with throttle barely cracked). If I kick it the miss is not apparent. No light or error code. Does not miss all the time, may go days w/o a skip and then take a spell and miss bad for a day or two. Seems to be worse when tank is almost empty. I have replaced the fuel filter and all plugs & COPs with new Motorcraft parts from Ford dealer, no change. Also used several bottles of IsoHEET (alcohol) additive with no apparent improvement. My next attempt will be to remove and completely drain the tank next time it gets almost empty. Any help will be appreciated. Thanks, Jim