I've got a 2010 6.4 thats got a small idle surge. Its about 30 rpm it idles down mainly notice it after it warms up. It acts like somethings turning on and it causes it to idle down. I'm deleted with egr disabled egr is still plugged in. About 8k miles on current fuel filter drained water separator about a week ago. Changed the fuel rail sensor under valve cover Saturday its still surging. Any help is appreciated. Doesn't surge while driving just enough to notice at idle.