My 84 Westy, with a 91 Digifant II (Jetta) engine, = has recently started puffing smoke. It has only done it going 70+ mph, while = cruising down the freeway it will suddenly hesitate and puff out a very = thick cloud of smoke, it lasts about 2-3 seconds, then runs as though nothing happened. Today it did it three times in four miles, I slowed down to 65 = mph and it didn't do it again. Anyone have a clue as to what might be causing = this? The conversion was done using Diesel parts.