Every now and then, when cruising at highway speeds. My car throws out a little bit of exhaust smoke. Just one cloud and then nothing. It doesn't do this regualarly. Very irregularly. Maybe once every 4-6 weeks. I can feel a slight stumble. very slight. Maybe less than a second. It was doing this before the boost control went in and it did this again this morning. I have checked everything out and everything seems normal. The car starts up fine in the morning. Even when it's cold it hardly takes one crank to start up. I blocked the EGR a couple of weeks ago. Could this be chunks crud in the intake braking loose and getting burnt up? If it is I'm gonna remove it and clean it. What are your suggestions. Other than this very minor problem, you could hardly call this a problem, the car runs perfect. It's due for a valve adjustment, 20,000 miles since last time. Could this help the situation.