Engine has no power and seems like it will choke

Here's what you seem to be saying. It does start when the engine is cold...cold enough to require choking to obtain needed fuel richness for starting. But then, when the engine has attained operating temperature, if you happen to kill the engine it will refuse to start. Logic and induction seems to suggest a flooding problem due to a choke that is not unchoking when it is not needed and is attempted to be released. So look to choke malfunction as the first problem needing to be resolved. Then, post again if the no-start problem still persists.

If the exhaust note sounds like a jet engine ,loud hissing,the catalitic converter has plugged. Makes the symtom you are speaking of.

indicates that the auto choke ( carby ) needs adjusting or if fuel injected , the ambient temp sensor needs replacing

If you recently changed the air filter you may have pushed up to ******* the top that is connected to the air filter hose and it pulled out a secondary rubber hose that seems like it goes into the top of what looks like the manifold at top of motor. I have a 2006 is250 I did that and engine choked and shook and check engine light came on I found the hose and reconnected it and it ran fine, to rest the check engine light you have to disconnect battery and reconnect and it clears it.

The choke light is connected to the choke and the oil pressure switch.
The choke coil is heated electrically and from the engine heat to make it open.
The heater could be faulty and the choke is not opening fast enough.
It may have had a Rochester Quadrajet when new.

Check ALL vacuum hoses as your truck is getting older and rubber components may be breaking down.ALL sensors need good connections,electrical and where needed,vacuum to send correct data to the computer.
Has the throttle body been cleaned lately?
Don't overlook regular maintenance,plugs,wires etc.

check the engine codes first that will be needed to diagnose the problem. no there is no choke on your truck

Your choke is working to good, to much fuel not enough air, if smoking after engine is at normal engine temp.you need to have coolant temp. sensor or your map sensor check, both act like a choke, you'll need to do a computer scan, also have engine check for a miss fire, well also cause a rich problem.

it seems that the auto choke setting is maybe wrong or there is a problem with engine management, or a worn part which is sticking.

when cold, the engine should be higher as the choke will be on but a warm up idle of 1200 seem a bit high i would expect around 800 and then on restart if the engine is warm then the choke should be off but the idle being too low indicates one of the above.

One problem is related to the other.The dieseling is caused by a rich air/fuel mixture which is caused by the closing choke.So you need to adjust the choke to where it is slightly open when the engine is cold.If it is electric then it has a thermostatic device that positions the choke just cracked open when cold and slowly opens as the engine heats up.Whats happening is the choke may actually be loose and when the engine shuts off the vacuum pulls the choke close creating the combustable rich fuel mixture(if you watched the choke when someone else turns off the engine you'll see the choke flapping while the engine is dieseling).Try putting a screw driver in the carb(with engine running) blocking the choke from closing.Then shut the engine off.It shouldnt diesel.You may have to replace the carb thermostat