Square Exhaust Smoke??

Something I recently found on the default C172 and have now seen in other piston planes. The "Start-Up" smoke from the exhaust now appears as a series of squares instead of the more realistic effect I've seen before. Possibly another SP2 thing I just had not noticed before.I am also getting square, black waves when I use the F12 key to look down on Saint Maarten,Anybody know a silver bullet for this one?Regards,ThraketeVista Home Premium with SP1, FSX with SP1a and SP2, NVidia 8600 GT factory over-clocked with the latest (May) drivers.