It still sounds like water in the fuel. When the rpms are higher, the miss is undetectable, but when slowing down, it will be noticeable. Turns, or curves will accentuate the issue with water moving around in the tank and getting sucked up. I would add at least two bottles of water dispersant/fuel injector cleaner type additive to the tank when it is low of fuel, and then fill up at a reputable station that is not refueling the tanks while there. I would even add a can of cleaner with each tank for a couple of tanks to make sure any and all condensation is removed from the bottom of the tank. I always fill the tank full when refueling to lessen the chance of moisture/condensation forming between fill-ups. Joe-JDC