Thick white smoke after decat 1.8t 20v

[James Tucker]

I installed a 3” downpipe + decat yesterday and all was fine except I couldn’t get my lambda & 02 sensor out of the old cat. Now the car is chucking out really thick white smoke and a lot of it at idle and in 1st gear but then seems to clear after getting higher up in the gears. I’m hoping it’s something to do with the air/fuel ratio but need a few more opinions on it.