sudden acceleration...Scary

[Overdrive]

Maybe a dirty or otherwise gummed up sensor for the pedal? Have you been running the A/C? I know my car tends to have a slight idle jump to compensate for the load when the compressor kicks on/off, but not as high as what you're saying.

Does it only seem to happen when the vehicle reaches close to operating temp and when the vehicle gets up to highway speeds? Does it do it at any other times?

Any other issues you've noticed, particularly of the electrical variety? If so, I'd say maybe grounds and/or ignition switch.

Either way, if you don't find the culprit soon I'd say bite the bullet and get it to a dealer or independent specialist. It'll end up costing you a lot more, and not just financially, if you lose control of the car and damage it or another person's car and/or injure yourself or someone else.