I am having problems with my 93 D350 stalling when I am decelerating. If I slowly let the engine rev down then it wont die. Otherwise it sounds like the engine is being choked before it dies. Always starts right after...so far atleast.

It has been doing it once a week for a few months
I just took the fuel tank off while I was welding a new bed. Ever since putting the tank back on it has been giving me problems every time I go to downshift.

I have a video but it wont let me post it.

 

You are getting air sucked into your fuel line from the tank to the engine, would be my bet.
Start with the location you just took apart and re connected to pull the fuel tank.