B3000 Truck idles rough at cold start-up.

Hi, my truck a 1994 Mazda B3000 3.0 ltr. F.I. V6,170,000 miles, idles rough for the first minute or so at a cold start-up. After it senses that it's starting to warm-up the fast idle drops quickly and tries to die on me.
It just started to do it one morning when I was getting ready to go to work.
Normally when I first start my truck it goes to a fast idle at about 2000 rpm's and slowly drops to about a 1000 rpm's as it warms-up. This usually happens with in the first two minutes of start-up. But now when I start it up, it goes to it's normal fast Idle but then quickly drops and tries to die on me, so I keep tapping the gas pedal to keep the rpm's up until it senses the engine starting to warm.
I can see several sensors from the air intake to the carburetor but I'm not sure which one or ones would be the culprit.
I did attach a photo to show the engine and the one sensor by the top of the engine, above the water pump thinking it's that one cause it connects to the throttle in some manner.
I also took off the black shield that was covering that sensor because it was hidden from view.
I stopped by a car repair shop and they told me it would cost a $120 dollars just to hook it up to a computer to tell them anything.....which I expected, but was hoping there was some way for me to troubleshoot it by some process of elimination.

So is this some kind of water heater sensor issue or idle sensor?
Any help would be dearly appreciated, Thanks!

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