couldnt this be a coolant temp sensor malfunction?

 

That doesn't sound right to me, although I'm certainly no expert. New info though:

It sat at work all day today (8 hours or so) and it ran great. I noticed that I could really nail it and no hesitation or hiccups. When the symptoms start, there is a slight hesitation or sluggishness to the increased RPM's...

Maybe that helps the diagnosis more.

 

i had really similar problems with my blazer. i changed several things i even checked my fuel pressure with came out good. but what it ended up actually being is the fuel pump. only problem is the pump costs about 300 dollars so its not cheap. hope this helps

 

Not sure about the temp sensor, however on a related subject.
Once warm, as in up to operating themp the O2 sensors information is read buy the computer and the puter uses that info to adjust the engines performance. It could be a fualty O2 sensor or a disconnected sensor. One way to rule them out is to disconnect them. If the truck runs great all the time, you found your problem. WARNING! Without the O2 sensors your truck willrun great, however your gas mileage will suck big time. Drive it long enough without the sensorsand you could end up frying your Cat as well. Too much raw fuel for the cat to handle.

Thekey to this test is driving while up to operating temp. Your daily commute of 3 miles isn't long enough. Its barely long enough toburn off the condensation. Make sure you change your oil at 3,000 mile intervals. No doubt you have white milky stuff on your dipstick tube. Take that bad boy for a half hour cruise and see how she does.

On second thought, your temp sensor could be part of the problem. Your truck has two temp sensors, one for the dash and one for the puter. If the one for the puter is shot then your puter will never go into closed loop mode (read the O2 sensors) and make adjustments. you could be dumping so much fuel that you are frying your cat, or have partially plugged it up. The test for th plugged cat is banging on it, if it rattles, replace. Another test is a half hour cruise at interstate speeds in third gear (higher rpms then OD). If she handle that it isn't plugged. No worry about driving in 3rd gear, its recommended for towing. Only down side is your not getting the best gas mileage.

 

I had a similar problem with my blazer and it was a wire (3-4 pin) that was replaced leading into the manifold, I'll look at my receipts when I get home, maybe some one else know what im talking about.