i had the same problem with mine and never found out what it was, i hope you find out as i still got my s2 in the garage

i remember it did my head in getting in and out the car (ALL THE TIME) turning the throttle up and down plus i had the starter problem were it wouldn't spin when warm so i kept getting stuck at lights looking like a nob

GOOD LUCK YOU WILL NEEED IT I TRYED EVERYTHING!!!