Hi guys sorry to post been looking around can`t see anyone with the same issue

Car is 2.0 t quattro 54 plate 2005 reg date remapped stg1 38000 miles

my bro inlaw noticed the other week when he followed me when i put my foot down bit of black smoke out of the exhaust is this normal?

it only seems to do it the first time i floor it and seems clear after that just a build up of crap? as i do pure town miles in it