7.3 starts, idles , runs at speed good but sputters at slow speed
 

I have a 2003 7.3 powerstroke with a DB tuner , truck idles and run fines but when slowing down to stop sputters and jerks like it is running out of fuel and will also do it when trying to put it in reverse where it will stall out. Someone had suggest it to be the ICP sensor so I changed it the other day with no change . The fuel filter is relatively new but I did almost run it out of fuel around 2000 miles before it started to act up .
Any suggestions or advise greatly appreciated