Running good until suddenly lost power and running crappy.

Car now running rough and loses power, sounds like its one or more cylinders.-- Upon acceleration, extremely sluggish, sounds like its missing or misfiring or timing is out of whack. I changed distributor, it was a bit dirty and worn, no change in running. The car was fine up until it chugged once at a light and that's right when I think I smelled a strange burnt smell, wasn't sure it came from my car or truck in front of me. Car seems to idle ok, but when put in forward or reverse, the rough running occurs.