HELP! SERIOUS STUTTER!

[georgeb]

You might have too much Gumout for the amount of gas.

[TheresGabe]

So this morning I was driving... In 2nd gear between 20-25mph the Festiva shuttered. Kinda hiccuped. Once I was going faster it was fine. It kept doing it in 2nd. Drove it a while, and it started doing it in first too! The on the way home it was stuttering clear up to when I was doing 75 on the freeway! The only thing I could think of is that I put a bottle of gumout fuel system cleaner in it, and i put it in AFTER filling up my last tank, instead of before.

Any ideas what could be happening?