replaced pmd now having new problems

i have a 98 sierra 3500. 6.5l 85k miles. when i first bought the truck i was having typical pmd problems. so replaced the lift pump and pmd as well as remounted it to the bumber. truck ran great for about 2 or 3 thousand miles. and then started having the same issues. she finally died on me at an intersection and would not start even after a day of letting her cool down. towed her. bought a new pmd and upgraded cooling fins. turned on immidiately and ran good for maybe 30 seconds. started coughing and eventually died but starts right back up and repeats the process every time. if i start it and keep rpms up shell stay running but coughing the whole time. i let it sit for about 2 weeks and came back to check for a clog in the intake and now wont even turn on. extra notes: my air conditioning stopped working a couple weeks before the intersection mishap. and when keeping the rpms up to keep it running i can hear the air pump working harder than usual. any ideas on the matter would be greatly appricated. thank you

Check all your grounds & cables. There are a couple that are hard to find. Passenger side on frame and beside the glow relay on rear of block. I have added a few more from batteries to block & frame. Do a search here . Also check your batteries are 100%.

thank you artwork i know its been a while since ive been on. im in the military and its hard to get 5 min to pop my hood let alone get on the forum. but yes thinking now its an electric issue and possible fuel issue as well. going to start with checking all the wires from ip to the pmd hopefully find some clues. and i should be able to run some codes as soon as my friend comes through with the machine. the thread from CCC has been very helpful almost an identical situation....... o and taking out the huge mouse nest under the intake manifold probably helped aswell. he found a nice home with my block heater wile i was in boot camp haha

Good luck seank, maybe if you get yours running, I will know where to look next! I WILL say this, the help here is amazing! Every time I am ready to give up they always give me another good direction. I am sure you are not as mechanically challenged as I am so they will get you fixed right up.

Did you install a PMD resistor in either if the replacement PMD's?

Was a heat transfer pad or heat transfer paste used between the PMD and heatsink?