I have replaced my idle air control valve several times but I keep having issues with it and when I do my transmission shifts really rough. Does anyone have a clue what else could be going on with it?

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I cannot find any vacuum leaks, I have replaced the map sensor and throttle sensor. I have noticed that many times when the idle control valve acts up it does it when I let off the Excelerator for a stop sign or stop light after traveling at hi speed. But it’s not always the case. Yesterday it acted up again and today I removed the third idle air control valve to inspect it. My truck had been idling very fast and shifting rough since yesterday. I could not push the plunger in on the newer idle air control valve so I replaced it with the old one from before. I pushed the plungerIn before threading it back in and now my truck is running fine again and shifting normal. But I have been through this before and I know it will not last long and the problem will reoccur. Can anyone tell me where to look further to find what is causing this problem?