My sister's Neon did that when the fuel pump was on its way out, when it acted up I would smack the fuel tank, and it would get right for a little while, but go back to lagging, every time I smacked it the thing would act right, when I changed it, the problem went away. Not saying that's your answer, but it could be. Keep in mind that's not the safest thing to do, homie. Good luck, wish I had more info for ya.
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