How would my Escort Cosworth act if my Lambda was broken???

My car startes perfect.. cold and warm but it startes with VERY BLACK smoke (for about 30-60 sec) and when I give some throttle I cant see any black smoke.. might the pressure that blows the smoke away.

If you say overfuelling well ok.. I am very sure it uses some more fuel than before I noticed something was wrong and my rear bumper got very sod black around the exhaust, but it dont cut or do limp mode.. and it boost with no problems.