Did you check to see if the exhaust was plugged? I can't imagine an MO2 at 5 mph.......I've never seen that.
First,you always gap the points after cleaning and filing them, if needed, at .012- .016" thousandths of an inch.
You always replace a spark plug at the first sign of trouble,too.
Make sure the airbox isn't clogged with a wasp nest or something aND MAKE SURE THE CHOKE LEVER FLIPS UP(OPEN), when you roll open the throttle after starting it. A stuck choke definitely causes excessive smoke and allows NO acceleration.
I may be taking a 240 mile trip tomorrow on my Sebring with an MO2, and I expect at least 35 mph,when I call for it. don-ohio (:^)