I gave up reading this after page 4, but here are my two cents.
I had a Scion FR-S. They are notorious for cricket chirping noises from the direct injectors. I used MMO with every fill up, approximately 4 ounces. I significantly reduced the chirping from the injectors. If I went a couple tanks without it, the noise came back.
MMO at this point in the game serves mainly as a UCL. It might have some minor cleaning ability, but I used it in the FR-S to lubricate the fuel system, which in that instance with that vehicle, provided a quantifiable benefit.
Now, in my Mustang, I have so far observed no tangible benefit to adding MMO during fill ups. Actually, the only thing I have noticed is that my fuel economy has dropped...but I don't have a substantial long term trend to really tell for sure.
On an aside, I used an MMO and Techron combination after I first got the car. Boy did the car not like that lol. Stumbling, hesitation, and misfires. Went to the dealer, who identified a TSB for a known issue. What was interesting however is that while I could get the car to present the issue without any fuel additives in the tank, as soon as I added them the misfires became immediately apparent in all driving conditions. This tells me that the fuel system on my Coyote may not be too keen on adulterated fuel.
After they performed the fix (new crank position sensor with O-ring), I no longer have any misfires, even with fuel system cleaners.
So once my MMO bottle is empty, I won't be buying anymore. Instead I'll just do a bottle of a PEA laced cleaner before every oil change.
As a funny side story, anyone who is familiar with the new capless filler necks on most Fords can relate to this.
I took a bottle of Techron and attempted to pour the contents into my Mustangs filler neck, only to watch a river of injector cleaner come pouring out behind the fender onto the ground.
Ford includes a small plastic funnel device for opening the filler neck. Without it, there is a valve that stays closed preventing the insertion of bottles all the way into the filler neck.
Gas pump handles are sized appropriately to actuate this valve on their own.
Prior to this I had been wondering what that white plastic device was for...