I have had EF and EL computers do all sorts of weird intermittent rubbish, they have stuffed me around big time before. While I agree that they would want to be the last thing you try, due to the cost, I wouldn't rule them out (not saying anyone has said this either, just to be clear

)! They owe me many an hour of hair pulling and frustration! And a few hundred bucks.... not my car personally, thankfully....
Cheers.......... Tim