The ECU pictured (XM w/PRV) is a pretty typical one from what I've seen in that it has a smattering of electrolytic caps.
My assumption - and I love starting with assumptions - is that these caps are chosen because of their specific impact upon a signal path or input form.
What is the possibility that, after twenty years, they are well past their prime and may not do their job so well?
I'm raising this because of personal observations on a couple of cars that seemed to defy thorough examination of the inputs and general conditions. Good compression, good sensors, good connectors, no corrosion in the harnesses, no change with sensor swaps - yet the engine might display slightly poor running when you'd think it shouldn't.
So - has anyone experimented with replacement, and if so were there noticeable changes?