Truck sat for a few months. Drained tank new gas. Now if I run to a store. The truck runs like crap on the way home

 

Is the temp gauge getting up to at least 1/3?

What year is it?
1900??

may need to borrow a OBD II reader and check to see if ECT sensor is working, it tells computer engine temp(not connected to dashboard gauge).
If computer thinks engine is still cold it will run it too rich.

How is it at highway speed, any lack of power above 2,000 RPM?

 

Sorry 1990 haven't got it up to highway speep. When I push the petal anymore them maybe 1/3 throttle the rpms go up and down.

 

1990 would be OBD I so not much help with reader unless there are some history codes in there

I would check the MAF(mass air flow) sensor closely, clean it, but also check the wires.
It reads like computer doesn't have a stable reading on air flowing into the engine, this could be from MAF not reading air flow correctly or from an air leak, in the MAF tube to intake or a vacuum leak.

Unplug TPS(throttle position sensor) and check its connections for corrosion.

If you have an EGR valve, with engine at idle remove vacuum line from the EGR valve, it should have no vacuum on this line at idle, if there is vacuum then EGR control module is bad.
Put another vacuum line on the EGR valve and suck on it, engine should start to stumble, if not EGR valve needs to be replaced and is probable stuck open a bit.

After(or before) any of this, unhook the Negative battery cable for at least 5 minutes.
This will cause the computer to Reboot at next startup, this erases and bad info as far as fuel/air mix and learned sensor data, so computer will relearn any changes you have made.