the way to check and see if the oil cooler is flowing properly is to watch ect and eot. if they are off more than 20 degrees, the oil cooler passages are restricted and will cause repeat egr cooler failures.
i have replaced egr valve upon egr valve due to backpressure pushing them open. and to do head studs properly guys, the engine needs to be pulled. the mls gaskets leave sealant on the deck surface.