4.3 issues

[pugs]

1st off, howdy everyone been awhile since posted anything.
ok so I snagged an 89 GMC a few months back and been having a few issues with now. did an O2 sensor, EGR valve. yesterday it seemed like the thermostat wasn't opening at all so I went and replaced it. refilled the radiator and such and let it run and it all seemed good so after the grand daughter left I took for a ride to the store and back and again its like the thermostat isn't opening. kind of wondering if maybe I don't have a head gasket issue. any ideas ?

[Palf70Step]

With cap off radiator can you see fluid moving, if so thermostat is opening. What makes you think it is not opening, Gauge? Do you have infrared temp sensor gauge/unit to see what the actual temp is?
The only thing I ever had was one time I didn't get all the air our of the system when I was changing my coolant. Once that was clear all was good.

[pugs]

I have it running now and did get some more out of the system. but then when I drove like maybe 10-15 miles the truck starts acting up and it stumbles when I get on the gas.

[pugs]

just took for a ride again and now the check engine lite is on again, code 32 EGR. and the upper hose is hard like the new thermostat isn't open.

[Tx Firefighter]

Is it overheating ? Any talk of thermostats is academic unless you can confirm that it's overheating or not. An IR gun is invaluable for this. What temperature is the engine running and is coolant circulating ?

Stumbling when it's warmed up ? Don't look at the thermostat. Look at fuel pressure first.

EGR code ? More times than not it's clogged passages in the intake manifold. Lots of people waste money and replace a perfectly good GM EGR valve for a Chinese part when the valve is perfectly fine, it's carboned up passages in the manifold.

Buy no more parts until you diagnose what problems you have now. Shooting the parts cannon at it parts introduces more variables into the equation and wastes money.