Rough running

[Sharpy]

Hi, asking if anyone knows why my 81 244 runs rough at idle untill warm then is sort of ok. Its hard to start and runs rich when cold(needs half throttle) like its running on 2 cylinders but all the exhaust are warm. Al so the brake warning light has come on and wonder if this is the same problem as it goes of when i put it in 2nd gear (auto) down a hill and create more vacume., Does that make sence . Thanks Don Please ask for more info