Well, thanks for being a good sport with what may now seem like a snipe hunt. 
I eagerly anticipate hearing what your tech comes up with when running the engine above 40. Unfortunately, I think this a case where the diagnosis will be "bad Processor Board"...as was prescribed in Engineer-Joe's case and the others you found in other threads. That is, I don't think the typical tech in business can "afford" to perform component-level diagnostics and repair for this type of problem. It only makes sense for a DIY-enthusiast where this is part of the hobby as opposed to a dollars-and-cents proposition. So even if the problem could be solved by replacing a $1 component, it's going to "cost" much more to engage someone else's services to identify the component.
