Mine also failed the HC at idle and was running rough and rich. Nothing seemed to fix it until I swapped out the injectors. You seemed to have tried everything else.

If it leads to desperation, why no make a small vacuum leak so that you lean it out for the test since it's only an 2 speed idle test and no load.

Also, if you've replaced all those parts, isn't that enough to get the $400 one year thing?