Truck was stalling.cleaned the egr valve and it ran fine.

I went through this problem, and did everything you did, even the SeaFoam. Turns out, the new distributor caps I bought were defective. I switched it out to another brand, worked for a day and then sputtered again. I read somewhere that (FOR THIS VEHICLE) aftermarket caps and rotors aren't manufactured correctly, causing arcing. Switched the cap and rotor to AC Delco brand, and all ran good, going on 1 year now with no problems.

Compression, spark , timing , fuel for any engine to run. Don't forget a stopped up catalytic convertor will have the same effect as you described. Backfiring of course is fouled plugs, bad plug wires, look for arcing from wires when it is dark outside. If it has a distributor check for cracked cap, had my 91 GMC start backfiring then die due to ignition module inside distributor going bad. It would start back up after it cooled for about 10 minutes.

I actually had to replace my EGR valve and the gasket. I clean the valve well and reused both. I don't think the gasket sealed well enough though. So I went ahead and got a new valve, gasket and changed them. It runs a lot smoother now.

Sounds like secondary ignition to me. When was the last time you chenged the spark plugs, cap, rotor, or spark plug wires?

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Hi,
Check the ignition distributor cap and clean the electric contact points it might be already dirty.

if one has a spark that means your ignition coil is still okay. Remove the whole cap and check the inside part and clean it, use emery board.
Check also the high tension wires( spark plug wires ).
Hope Fixya helps you!

http://groups.yahoo.com/group/villagerquest/

clean MAF sensor heated wires with spray carb cleaner first

spark plug wires. rotor, cap, clean the spark plugs, and make sure you have the correct firing order

tune up is likely what you need from description

friend if it backfire then you must check your oxygen sensor to see if your engine running rich , thats mean too much fuel cominng to it , more dangerous thing is if you have a leak from the intake valve . finaly your sparking plugs may not firing well in some cylinders that makes unburned fuel to comes out from the engine to be burned in the exhuse tube.

Its just fouled some plugs again. Need an overhaul. If you just put a valve job on it it will just put more stress on the rings and will need it anyway. Not much you can do except change plugs all the time!
God Bless Greg