Finally got our ride back. Apparently there's a bad batch of ECU's that got past quality control. After trying to put in a new one without success, it was discovered that Toyota Canada had labelled it for manual transmission when it was actually for automatic (at least that's what the dealer says). Once they figured that out, they had to order the right one. But by that time, the ECU was on backorder, so we had to wait for what felt like forever. So they finally got the right one in, and it's been working fine for two days (knock on wood). But now we have to bring it back in to get them to repair a gouge they made on the dash, a scuff they made on the door, and a horrible rattle behind the glovebox that wasn't there when we first got it. This is all sooo bloody frustrating!
And no, we didn't try any mods before all this started, and will be holding up on doing anything until we know for sure that this car won't crap out again. The only thing we've done so far is to replace the whimpy horn with something that doesn't embarass us to use.