93 K1500 4x4 - 350 engine, it taps when runnig hot and lose power

I have this problem, every time I drive long distance - I would drive for 2-3 hours fine and then when I slow down to get gas or food, I would notice the very loud tapping sound from the engine, and then it
gets even louder if I step on the gas try to increase speed. It feels like the engine has lost all its power when this happens.
If I shut the engine down for a while - 30 to 60 minutes or so, and then start the engine backup, the noise would be gone. And this repeats after I drive another period of time.
When I am in town driving around, it does not happen.
Last week I changed the Recirculation Exhaustion Valve (I think that was what my mechanist called it) and he told me that (bad valve) was what made the tapping noise when engine runs hot.
But it still happens when I drive on long trips. I check my engine oil, coolant, all seems to be ok.
Any idea or advice will be greatly appreciated.
Jack
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maybe if you could read mores code, .haha, it is trying to tell you to stop for a drink or something. LOL old john

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Sounds like a worn rod bearing or two. The oil is the thinest and hottest when you cruise the hiway for a while hence the knocks after a long run. If you are using 5w30 oil STOP!!! Try a fresh oil change with some 15w40 (not 10w40) and see if that helps. If it does and it should, it confirms that you have some worn rod bearings. The good news is that you can replace the bearings if need be without pulling the engine and extract some more life from it. You do not want to let this go because if it is worn bearings it will damage the crank with time to the point that the engine will have to be pulled to properly repair the crankshaft or to replace the engine.

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Snoman, thank you so much for the information. I will have it checked right the way.
Jack.
SnoMan wrote:

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Jack wrote:

==============Check your spark plugs and suspect carbon buildup on the pistons.
a guess.....
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