u/FineAd1224

hi there! me and my fiance just left the house and at a stop sign near our home, their car rocked back and forth about 2 times when it was stopped before they put it in park to make it stop. apparently its happened once before and theres been a stutter when they accelerate for the past few months. they also had a check engine light that went away so we assumed it was just emissions since they had just gotten their muffler done. it then reappeared awhile ago and has stayed since.

what could this possibly be?

edit: forgot to add that they have a blow off valve and a cold air intake