I'm replying to your follow up question about the IAC valve here, because they will certainly delete your follow up question; as it was posted as a new topic, when it really is a continuation of the original thread. The only way a follow up message can be posted is to click the "answer this question" button under the original question. If you post it anywhere else; it will be deleted.
Cleaning the IAC valve is likely to correct the stalling; as might all the other items I suggested. Since that valve is so expensive; it is preferable to clean it and its passages than to replace it. I also want to add one additional item, which may also be likely to succeed. It is called the PCV valve. A clogged PCV valve or its hose will richen up the mixture, and lead to stalling.