I just removed my stock cat ( huge pita ) and replaced it with a resonating MP. One thing I noticed was that with my high mileage engine (128K), I would always get a fair amount of white smoke coming out from the exhaust for a few minutes during a cold start. When I cranked the engine with the MP to my surprise there was no white smoke! What's up with that? Does the stock cat hold that much condensation? All this time I thought that I was burning either oil or coolant. ( although I never smelled coolant, only rich exhaust)
I thought I read a previous post and someone commented the same observation. Has anyone else experienced this and know exactly why this happens?

 

I just did the same.. and yeah I'm waiting for the smoke to start. Yet haven't seen anything. I did a DP and a MP.

 

all the cells inside the cat create a huge surface area for condensation to collect on, so although i am not sure - it is perfectly possible that the smoke you saw was condensation from the cat.

 

What's funny is I've had opposite experiences on FC's. On non-turbo FC's it's not too uncommon to have bad oil seals in the motor. In that case you get less smoking with a cat, as it seems to collect the oil and burn it off slowly, or burns it hotter, or something . With a straight pipe it's a smoke show.

But, I'd vote for the condensation on your car.

Dale