i have an '02 WRX that is all stock with 158k miles on it. when i am in traffic at speeds under 30 mph it seems to jump excessively right when i engage the throttle and a little bit when the throttle is released to coast. it happens mostly in 1st gear at midrange rpm's so around 10 - 15 mph. is this normal? if not, what might i need to check and/or fix?