Computer 101 please

[stock89]

Fellow enthusiasts,
My car has had a rolling idle problem, actually it sometimes just goes to 2500 and stays there. First I cleaned the IAC, then replaced it (from Ford), the TPS, and TB. Nothing seemed to work for more than about a week or so. Then I realized that it's a complete random problem. If I disconnect the IAC it runs fine.
If I disconnect the battery for an hour, it'll run good for about a week. Then the problem comes back.

So now the dealership says I need a new computer. The problem, they say, is they aren't in the inventory any more. Is that BS?

Will any computer from the junkyard work? Do any of you have a computer sitting on a shelf you don't need anymore?

Thanks,
Rob