I figured I would post my work in progress here and maybe it can help someone else out in the future. I'll outline this in a bit more detail.
Two months back, I started having problems with the Fusion making the farting noise. I changed the charcoal canister next to the gas tank, and that problem went away for a couple of weeks. After that, then I started having problems with the car stalling at red lights, and, the farting noise came back occasionally and in several cases, I heard it while going 40+ mph in some instances. When I could hear it, I knew I had to pull over somewhere safe and relieve the pressure on the gas tank cover by pushing it in. Sometimes that would help and I could go on my way, but most times the car would stall anyways and it would take 5-10 minutes to restart the car and get going.
Well, I was finally at my limit of dealing with it and I ordered a purge valve through Parts Geek, but got the wrong part which led to my initial post here (the part is different between the 2.0 and 2.5 engines). I have since gone to the Ford Dealer and got the correct part, and everyone calls it something different so that's half the battle with this. The part I got is more like a tube assembly with connectors on it and a valve. I got the part out of the bag and played with the connectors to learn how they work. That bottom connector which is yellow in color looks like a PITA to install. It almost seems easier to drain the antifreeze out of the car so you can move those antifreeze hoses out of the way for more clearance. I looked and contemplated for how to do this the last couple of days. Yesterday, just for giggles, I looked a little closer at the green connector that attaches at the valve that is currently on the car. I noticed there was a bit of a gap between the connector and the valve. I disconnected the green connector and moved it closer to the valve, figuring that it couldn't hurt.
That said, the Fusion has ran better today than the previous few weeks, including better gas mileage and no rough idle. Best yet, I was able to fill up the car with gas all the way to the automatic stopk and the car started right away for the first time in a long time.. I didn't have to wait 5-10 minutes for it to start. Now when starting it sounds like it used to when new. So the moral of the story is you may not need to change that tube after all, but check and make sure that connector that attaches to the valve is close and snug. I had the oil changed and the battery replaced around the time all of this started happening, so maybe that tube was disconnected to make getting the battery in a bit easier, or just normal use, who knows... but this tip might save you some money, or more importantly your life. The car would stall out on me, and worse yet when my wife was with our daughter in the car. I could care less about the noise, and I tolerated the car's behavior even when I knew the engine was going to die from hearing the noise. I have no doubt if I would have brought it into a shop somewhere, dealer or not, I would have been paying for parts, diagnostic fee, labor, and who knows what else and all it seems to be was that the darn connector wasn't seated well because of poor design or some flaw. Now, if the 15 Fusions are recalled like the 13s, I've bought the part and can get reimbursed.
I hope this helps someone else having this issue, there are a lot of us with this problem with other models of Fords, not just Fusion owners.