Backfiring through exhaust when engine is warm

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That sounds like a bad egr valve or a bad egr solenoid. Two bolts to remove takes about five minutes to swap. Unplug the egr vacuum line and put a cap on the line to keep it from leaking and take it for a spin.

 

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Well got off duty this morning and broke out ye old pressure washer and a bottle of engine brite. My driveway looks like the Exxon Valdez right now lol. So much baked on grease on the frame and hoses. Discovered to my odd satisfaction that the lower radiator hose is a gm hose... wouldn't be surprised if it was the original considering everything else I've found. It's about time for a new belt, has some cracking in it so that job is pending for next payday. Not one bit of rust on the frame surprised the hell out of me to say the least though, but having a running undercoating maker namely the oil leaks, probably has something to do with that!

 

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So it's a bit early but I think I solved my backfiring issue. I filled her up this morning since I've been out to sea for the last week since I did my heat sink paste repair, and put about 115 miles on the old girl. She didn't pop once today. Did a mix of stop/go and hopping on and off the interstate. Gas gauge hardly moved either unlike before so I think she was misfiring even before she would backfire and was wasting fuel. So for the time being this puppy is considered SOLVED.
Parts replaced-
Coolant temp sensor and switch
Thermostat
Iac motor
Egr valve
Throttle positioning sensor
Heat sink paste compound
Spark plugs wires cap rotor pcv
Throttle body rebuild kit
Every damned vacuum line under the hood!!!!

Everything helped in some way shape or form. It I conclude that the ignition module was heat soaking due to lack of thermal dissipation.
My next thread will be the valve guides when I do that next month. Expect pictures along the way!!! Thanks to everybody for the assist!

 

[Breakdown]

Well wanted to give the true final update on this thread. Conclusion was the thermal heat sink paste on the ignition module. Drove on Friday from Jacksonville Florida to Aiken ac (390 miles) without a single hiccup. Averaged 19.8 (corrected with gps) on the interstate 17.2 on the back roads/in town. Just wanted to put it out there in case anyone was following the thread. Truck ran like a CHAMP!!!