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... you'll love these little machines. Your problem could be any number of things, from needing a new fuel filter, to spark plugs, to ignition coils, etc.
Since your MPG gauge is jumping a bit too, it makes me suspect ignition coils as I've seen this happen before. Their tach was jumping around too though. So right now I'd say to check your spark plugs, and ignition coils.
However, we'll need some more symptoms to narrow down the problem though. Like does it stutter than you floor on the gas at any time? Are there any sounds you hear while this happens? Backfiring? Tach dying? Lights dimming? Does the problem go away when you release the throttle?
Let us know a bit more information and we can help pinpoint your problem.