WATERGUY- doesn't sound like turbo to me. you probably wouldn't be able to get the truck up to top speed if your turbo was having problems.
however, have you gone through your air intake system to be sure it's not blocked in any way. getting too little air, may leave unspent fuel in your heads, but i doubt it.
in the situation you described, and with my theory, running the engine hard might be sufficient enough to burn off the excess fuel because you are at higher rpms. by time you get back home and idle, the excess fuel begins building up and eventually floods the engine once in idle.
if it doesn't die in idle, and you try to shut it off, but there it's still cranking, that's not because of air. it's because of fuel.
if the only thing going into your engine was air (assuming that the turbo was pumping after you cut power) there would be no combustion.
instead it sounds like excess fuel is getting into the heads, which keep turning, which as normal sucks in air, and continues the combustion process until the excess fuel leaking into the heads is consumed.
then the engine dies as you describe 20 seconds later after shut off. or quickly due to flooding.