It is advisable to keep the shock absorbers plates as high as possible. This because the air, due to the vacuum effect, goes upwards and therefore even if there will be bubbles under the piston, with this heads up they will be easy to remove. In case of shock absorbers such as PSS where the plate has no holes, it is suggested to repeat the procedure a couple of times to make sure that all the air, even the one under the plate, can be removed. As for the diffs, it can be placed directly in the center of the device in the dedicated hole. The vacuum obtained with AirKiller+ has a hold of several hours and this is excellent for diffs with very high viscosity oils. We still recommend if you are going to extend the treatment by pressing the start button again which will get back the vacuum effect at the maximum values. If you try to restart the pump, once you get the vacuum, and this doesn't work, don't worry! It means that the vacuum is already at the maximum value.