I've noticed on mine it happen's when it doesn't get enough revs. I don't spray it in and leave to sit as a lot of the stuff just leaks out of the nipple. What I do is after the car's warmed up I just pull the hose off and start spraying getting my nephew to keep the revs between 2000 and 3000. Mind you I use 2.5 cans every time. When he's on the lower revs no smoke but as he increases the revs to 3000 she smokes away. Towards the last half can I don't get any smoke at all.