What part controls shift and acceleration and how much does it cost to replace?

I've had this problem off and on for several years and the Firestone shop I took it too said I didn't have any problems. One of the most disturbing features of this acceleration or deacceleration issue is that sometimes my car acts as though it has cruise control and it doesn't......accelerating all of a sudden or braking while on the highway. I had a mechanic tell me that shorting the cables would "reset" the chip and it has but we wonder how long we can reset it before something has to be replaced and how much it will cost. Don't know what chip it is but diags aren't finding it.