It was about 4 C this morning when I started the 993tt. Out of the right side exhaust there were clouds and clouds of steam like what you might expect from a cold dry morning. From the left side there was very little. Why the big difference between left and right? This isn't the first time I've noticed this.

 

My understanding is that much of the water vapor is byproduct of the cats so one of your cats may be dying.

Does it continue that way after it warms up, or just when the engine is cold?