I have a 1971 914 Porsche with a volkswagon engine. Motor was completely rebuilt 10 - 15 years ago. It only has about 2000 miles on the rebuilt engine. Has been in a garage the whole time and has been started every 2-3 months. Has dual weber carbourators instead of the original fuel injection system. This was done by a reputable Classic car mechanic. Now the car smokes excessively after 10-15 miles of driving when you let up on the gas pedal as in stopping at a stop light or sign. Does not smoke when you are excelerating or cruising down the road.