Intermittant dying- put in reverse and driving around town

Hello all- Hope this is in the correct forum-

I just purchased a 99psd (auto) and it dies every once in awhile, most times once its warmed up and i back up into my driveway. It will die, kinda acts like the convertor tries to lock when i put it into reverse and it dies abruptly. Put into park and it fires right up and backs up fine... doesnt do it all the time, just seems convertor related?

It will also shift into 4th around 40MPH and i need to press the button on the shifter to keep it from dogging in that gear, or sometimes it will die going down the highway if i let off the pedal at 40mph... put in neutral and it fires right back up and motors right on down the Highway.. Is there a way to control TCC lockup of the convertor? It seems to lock at WOT and runs out AOK.

Thanks in advance
BW

PS truck is down on power, seems to have a bad injector... it smoked alot of white smoke, ive been adding cetane and trans fluid to the fuel and the smoke is 1/10th it used to be and idles alot better now.... power is back up to where it should be...

BW