this really sounds like a vacuum leak so your tune shouldn't matter because it wont help with this situation...do you hear any whistling noises when you are under throttle or any sucking sounds that are out of the norm? These motors have a hand full of spots that are notorious for having vacuum leaks.
My last vacuum leak was right here...New gasket solved the problem. Cost like $2 and fixed my idle issue...all I had to do was press down on it and wiggle it a little and the idle would start changing. It would be worth unbolting this inlet and reseating the gasket to eliminate this from the equation...takes like 2 minutes.
Im also sure this was already asked "I didnt read every post" but have you cleaned the MAF...? I saw somewhere that it was descreened...