1987 Oldsmobile Cutlass • 200,000 miles

At first whenever I would turn the heat on the car would run sounding like it had an exhaust leak but I'm 95% sure I don't have one. Now it sounds like it has an exhaust leak ALL THE TIME, which is very embarrassing but still goes EVEN LOUDER WITH HEAT ON. Changed oil changed plugs and still loud. It's a 305 and I also have a problem with minor dark grey smoke and chugging when I start the car or idle long periods. Please help I love my 87 cutlass like my best friend. What's wrong with her : (
February 1, 2013.

If exhaust leak, check the exhaust. Maybe the muffler is worn out? How long since over-all tune up? Any applicable mil codes? You should be able to check those codes, yourself.

Does it use any oil between oil changes?

Clean throttle body and idle air system. See if it helps?

Feb 1, 2013.