It should mostly smoke when the engine is coming down to idle UNLESS you had quite an amount of oil burning. At that point you would notice the smell and it would probably have a bluish tint. I'm sure it is just water vapor. Also, you would see a hint of smoke right at start up. I noticed that on my car after the second time I tracked it. Wasn't worried about it because that was the only time I noticed it.
I wouldn't worry a bit about that amount of smoke if it indeed is. My Mazdaspeed 3 smoked a little when I put an off-road pipe on it and so does my turbo Mustang with straight exhaust. You wouldn't notice a small amount of smoke with cats.
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