1987 Honda Accord Smoke

I already received a response to this question below however I don't believe that it is the heater core. This is because there is no antifreeze dripping from the drain pan nor is there level going down in the radiator or an overflow reservoir.

Smoke coming through A/C vents. Car still runs normal. Smoke also comes from underneath hood normally when slowing to 0-5 mph after driving above 40. Has a burning or exhaust like smell. However I also have an exhaust leek so that could be what I'm smelling. It does not matter if the heater or A/C is on. I can normally avoid any smoke coming out from the hood or vents if I accelerate very slowly. However, if I accelerate very fast It can become so smokey in the cab that I have to roll down the windows. Does not affect the performance of the car what so ever though. Any other ideas?