last nite my engine managment light came on for about 2 minutes, i was shitting myself and hoping that it would go out. when the car is cold after a little rev the revs drp right down to about 500 and this morning it actually cut out. why is this? wot can be done without taking it to vauxhall and spending stupid amounts of money on it? its a 1.8 1998 sport if that helps. all advice much appreciated.