Racedoctor, believe me, I am 99.9% sure that your problem is what is described in the link that I and kaynd have provided. I'll try to give you a description of the few things that are happening...
First of all, with the Momo and DFP pedals (they are the same), the axis of the pedals are tapered. The first problem is that when you push the pedal, you can easily create a slight side force on them which will spike the pot past 100%. Beings a constant auto calibrating system, the drivers will see this spike and calibrate 100% accordingly. What that means is, the next time you press the pedal and don't get any side force on it, it will only show as around 90% or so. Locking the calibration in LFS does not help in this situation as it is in the drivers and the design of the pedals themselves. I have had this problem and fixed it with the link to Mozso's site.
The second problem are the way the pots mount into the base. It doesn't matter if they are revision A or revision B, it happens to both I have heard. The pots have a small nub on the bottom of them that get pushed into a slot in the base to hold them. They are prone to wiggle a little bit loose. The pots are mounted on the ends of the pedals in the center of the base, which means the wires are bundled up intertwined with each other. When the pots wiggle loose, you will press one pedal and from the wires moving, they will move the other pot. This is probably why you see your brakes come on after pressing the throttle. I suspect your pots are slightly loose and the wires are moving and causing the other pot to turn just slightly.
Don't disregard advise if you haven't actually looked into the advise. Unless you have taken the pedals apart, then you won't know. I have had both of these problems. The worst was a league race where when I had to brake I would get up to 50% throttle. Makes it a bit difficult to take a corner when you have 50% throttle as you brake.
The pedals are extremely easy to take apart and put back together. Besides the poor design of the pedal axis and how the pots are held in, it is a very simple design. It would take nothing to have a peek inside and see for yourself. But, just from openning and looking, you may as well do all the fixes on that site, which are very simple. All it is, is wrapping a single layer of electrical tape (black vinyl tape) around each axis to tighten up any play and securing the pots in their holders. I can't remember what the site recommmends on securing the pots, but some kind of flexible adhesive goop stuff would work great. I did the wedge a folded piece of paper to take up slack in mine and ended up eventually breaking off the nub. My pots are now superglued in, but I don't recommend that if you ever need to remove them.
