Idle problem 560 euro

[esuitter]

This is a 1985 5.6L AMG euro engine it idles high approx. 1200 rpm. When placed in reverse it loads down and holds about 650 rpm when placed in drive it also loads down to about 650 rpm BUT about 5 seconds after it hits 650 it starts applying power without touching the throttle and gets so aggresive I can't hold it with the brakes. This is a euro and has no electrically operated idle control valve.