[20vquattro]

Hi guys I recently purchased an Audi 100 turbo auto 1990 model - it's been fine until today when I approach a junction and slow down from speed the car idles funny and tries to run away from me whilst i have my foot on the brake. It then cuts out and i ahve to start the engine again??? Have any of you experienced this or know what it could be?? I would be very grateful

cheers 20vquattro (juneid)