Still caughing and spluttering!

Well got the car booked in to get a service and to get an MOT done tomorrow, but still having a few problems with the car :(

I thought all would be fixed when I got my new timing chain fitted, but still got a wee problem. At first I thought it was just a general Mini thing, but after driving the wife's R56 S, it does not have the same problem. Basically when I open it up in second, as soon as the turbo goes to kick in, the car chugs a little, and there's a puff of smoke comes out the back and then it finally goes, and if you open it up again its fine. Happens every couple of weeks or just under. Any thoughts?

I drive the car daily, but most of the time I don't get to open it up, so is it just blowing all the crap out and getting going seems I don't really opening it up that much?

Could be. Stick some redex in a tank of v-power, give it some beans, and see if it happens again. Hoepfully that'll sort it and it's not a turbo issue