2001 Monte Carlo acceleration problem!!!

My monte carlo just started to give me this problem. The car accelerates up to 40 mph by itself. The check engine light was on and I took it to the shop and got a diagnostic test ran on it. The computer said that the Induced air control valve and engine control temp. sensor were bad so the mechanic replaced those two parts. A day after it was fixed, it started doing the same thing again. I took it back to the shop and the mechanic couldn't find the problem so he disconnected the computer system and reset it. The car ran perfectly for a day and now its doing the same thing again!!! I don't know what to do!!

Post back the exact codes for help and as required, the engine size, and if pertinent any work done prior to this issue.