The EGR system in your vehicle is a differential backpressure induced EGR valve system. Which means some of the exhaust backpressure is used to force the EGR valve open. To control the pressure and volume of the exhaust gasses that enter the EGR valve, the feed pipe from the exhaust pipe to the EGR valve has an orifice that controls the amount of exhaust gasses that enter the EGR valve. If the orifice in this tube is no longer there from corrosion or is just burned away, too much exhaust gas enters the EGR valve destroying it. This will occur when the engine is under a heavy load because the backpressure is at it’s greatest, and the exhaust temperature is at it’s greatest. If there’s a restriction in the exhaust system, such as from a restricted catalytic converter or a restricted muffler, this will make the problem much worse.
So, make sure there’s no excessive backpressure in the exhaust system, and change out the feed tube from the exhaust pipe to the EGR valve to make sure there’s a good orifice in this tube
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