Truck spits, sputters, backfires

I have a 93 Dodge Dakota, 3.9, v6 and I recently used seafoam in the gas tank, in the brake booster vacuum line and in the crank case. I used in the gas tank first and ran it for about a week before using it in the crank case. I pour a whole bottle in and warmed the engine up, then I shut off the engine and it sat for 2 days before I had a chance to change the oil. After changing the oil, the truck runs fine when it is cold, but as soon as the temp starts to move up, it spits and sputters, backfires in all gears and I cannot go above 45 mph. any ideas? All so, I ran it through the vacuum line before I poured it in the gas tank, ran fine the whole week!

check the pick up coil in the distributor