have a 99 grand prix GT over the last year or so, while driving it will act like it has hiccups for lack of a better discription. it jerks and doesnt act like it wants to shift to the next level. i usually can push on the gas and it pulls right though. it doenst seem to be related to the weather outside at all. i have noticed that it does only usually happen when i get gas at a different spot other then my usual 2 places. As long as i stick to those 2 spots it doesnt happen. Is it the ethonal they are using now or should i be looking for another cause?
