I have a 1996 chevy silverado. 350 engine. Lately when I have been driving around 40 to 50 mph my truck starts to shutter a little bit or sort of slightly jumps. You can definitely tell that something is missing although it does not feel transmission related at all. This problem also occurs when I'm going about 70 or more, especially going uphill on the highway. I have a rough idle as well. I brought it into a garage and they said it was a leak in my intake manifold gasket. Would that be the head gasket? Wanting a second opinion I took it somewhere else and they said they couldn't find a leak. Has anyone had this problem before or do you know what the problem might be?
I trust my first mechanic, he does most of my families work. If it is the gasket, do those "gasket repair liquids" put into the radiator work?