I recently bought a 98' 2500 wity the 6.5l. Within a week or so I had stalling issues. The truck was sitting for some time when I bought it so I added some diesel kleen and changed the fuel filter and all was swell for 3-4 days. Then my issues started Agian and it would stall cold , hot, idoling or doing 70 on the highway but it would almost always fire right back up. My cold start up was painless as well. I searched the forums and all I see is PMD .... Everywhere I had figured this was my issue and that I would end up stranded one day if I didn't order one. My truck has 220k original looking pmd in stock location.

Well I got stranded Thursday conveniently at work ( I drive semi) so I had access to tools. What got me stranded was one of the mechanics I work with suggested air bubbles so I opened the bleeder on fuel filter while it was running .... And it died.... Fuel filter canister bone dry. Filled it with fuel from can , cracked injector cranked till it fired, put injector line back refilled canister starts right up... For 2 minutes . Died fuel filter canister bone dry.

I had a deing lift pump. The in line fuel pump located under driver seat in frame rail on my truck. .85% sure this has been my issue the whole time. Because when I changed the fuel filter before I had to manually fill the canister aka lift pump wouldn't do it.
Took me 4 hours to figure out it was the lift pump only 15 minutes and 80 dollars at nappa to fix it.( I know they are cheaper online I needed it now)

So don't get me wrong I'm going to get a pmd with relocation kit in the near future but its not always the issue with stalling. Might seem obvious to some of the guys on here but this truck acts a lot different than my semi and I'm no mechanic

 

A problem with a bad LP that helps kill stock mounted PMD's is that the system was designed to cool the PMD by the fuel flowing through the IP,lack of fuel helps overheat PMD's so don't be timid about having a spare PMD on hand.

Good work finding your primary problem.

Also check for excess vacuum in the fuel tank next time you fill up,plugged filler cap vents create excess vacuum in the tank and put extra strain on LP's that they sometimes can't overcome.