I have a 98 Dodge Dakota Sport with the 5.2L V8 Magnum. I bought it at 100,000 miles about three months ago and have since noticed that the tachometer fluctuates constantly. it doesn't matter if i'm slowly accelerating or on cruise control at 40, the tachometer looks like it's having a seizure. They're not huge fluctuations, mind you, only a few hundred RPM either way, but i'm sure it can't be good for my gas milage and I have no idea what is causing it. I've heard a faulty sensor and dirty fuel injectors suggested so far. I run a can of fuel injector cleaner once a month so i'm not convinced that that's it, but maybe. Any other suggestions or similar problems?