First for no apparent reason and without warning the idle dropped enough to make the engine die......... 300km from home! I managed to raise the low idle to allow it to stay running. Pulled the trailer all the way home no problem. Today..... I'm bombing home from work same as always and intending to see about dropping the idle back down. The truck "surges" revs on an uphill going about 130km/hr then smooths out. I figured it might just be "hitting the air pocket" since i was passing a couple of semis a the time. Got to my street and went to slow down, now it's idling really rough at low rpm. It smooths out some when I rev it up but i'm stumped! Could it be a bad injector? How can you check or tell?