I'm not a mechanic but was googling some problems with my car and it wasn't even 5 minutes ago I was reading an article that didn't apply to me, but sound a lot like the problem you're having. Read this:
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. There are 2 or 3 differentpost on that one page describing exactly what you are saying. Thosepersons have had their IAC and TPS changed and it did NOT fix theproblem. The answer to the problem was the below quoted suggestion.Good luck...
"This is a difficult problem to detect because the computer can not sense a malfunction, the vehicles computer system thinks everything is ok. In reality what is happening is the electrical component inside the MAF sensor becomes contaminated by air impurities. These containments imbed themselves to the electrical component that senses the air flow causing the sensor to be slightly off, but not enough to trigger the MIL (malfunction indicator lamp). Replace the MAF sensor with a new. NOTE: (Mass Air Flow MAF sensor or Air Intake Sensor AIS, depending on manufacturer. It does the same thing only with different names)."