The last four Airflow tanks I've bought have been such a tight draw that I've felt really sick and dizzy even with the airflow at it's most open. Bought two more today and exactly the same problem. Found a very old coil today which had come with an old airflow tank and noticed that the coils were different. The old coil was blocked off at the top but had holes in the side (presumably to allow for the airflow adjustment) but the coils in the four new tanks only had one hole at the top and no holes in the side. Put the old coil in one of the new tanks and it's perfect and the airflow now works. Why have the wrong coils been put in the airflow tanks?