? for a certified mechanic?

I had a bad exhaust leak manifold bolts were loose and no gaskets. Flange gasket was blown had 2 broken studs. Would that have any effect on my heater blowing cold air while at a stop sign? I fixed all that stuff and I noticed the car is alot quieter and idles alot smoother. I had someone tell me I could have a vaccum leak thats why the cold air at a stop. If you can answer my ? I surely appreciate it Thanks!