kungfu

i just fitted a turbo xs vta dv on my car. since this, when you go to plant the car, generally 3,4,5 gear, the car stops revving and almost goes to stall, when you let your foot off and put your foot down again it's o.k. you would almost think it wasn't getting enough fuel but it has done this with a half tank of fuel on board as well as almost empty.
help would be appreciated!!