1989 Toyota Pickup idle problem

I've asked a question on here before and you guys were a big help so here I am again. A little history. This is a 1989 toyota 4 wd pickup with a 3.0 fuel injected v6. Their are no modifications on the engine. Everything is stock. It had a few mods like after market headers and intake but it has all been removed and brought back to its original configuration. Everything works better that way. My current issue is when I start the vehicle it will fire right up and the idle will be a little high for about 5 seconds and then it will drop down almost to the point of dieing. It acts just like an engine about to stahl. If I just leave it alone the idle will go back up in about 10 seconds. At that point the idle stays a tad high until it warms up a little and everything is fine. It will do this only when it is started " cold " The idle will only drop real low one time. There is no cycling of this problem like up and down and up and down. Just the one time and after that episode everything is fine. I have replaced the coolant temperature sensor, cleaned and re-assembled the IAC, idle air control valve in the throttle body. Checked for any air pockets in the coolant system, checked for any vacuum leaks. I have checked just about everything that I can think of except the cold start valve and I am going out to check that as soon as I finish here. These older toyotas are famous for this and its not usually a certain part that causes it. I've read alot on it and even though the symptoms seem to be somewhat the same there is quite a variety of fixes. I attempt to keep my trucks in good shape, I have 2 of them. They are the same years just one is a king cab with full power and the other is standard cab with no power assist on anything and thats the one I'm working on. I could use any advice you guys can give me. You guys are awesome and know what you are talking about. I have no problem donating and would prefer to handle that part of it the way I did when you guys helped me with a previous problem a year or so ago. I based my donation on the information and help I received. I hope I'm not coming across like a jerk or a tightwad because I dont mean to be. You guys are great and any help is worth something. If I go out and and replace the cold start injector and that fixes it I would still send ya'll 5 bucks just for all the space I took up and for your patience in reading all my ramblings. Thank you guys in advance for being there to help us out. Your a blessing. Hope to hear from you. Russ.