People make mods they don't need to, there is no reason to cut the end off, please be more patient, I am trying to help but it does no good to get all frustrated, walk through it methodically and logically. It is a simple mechanical system, this is certainly solvable and not likely a technical defect. I have used this skimmer many times and have set them up at trade shows without issue and that is a very short time span to get something up and skimming but it requires an understanding of how it functions so I will explain it below.
First, water will always exit the small side hole in the intermediate chamber, the key is how much and that the water is not backing up to the level of the air intake nipple which is what happens when the antioverfoaming is activated, it can be helpful to bypass the antioverfoaming during initial set up and this only involves removing the air hose from the side of the skimmer body and bracing it up so it is not in the water of the sump or kinked.
There are 3 adjustments-
1) Depth of submersion, the deeper it is submerged the less resistance their is on the water column, think of it this way, if it was not plugged in, you would have that much more water already in the skimmer, the pump is free to add more easier. Lowering the water level can be one solution but at a minimum 1/2 of the actual motor, not counting the impeller housing must be under water, a good gauge is half of the label on the side of the pump at a minimum must be under water. If the pump runs dry, it will burn out. Initially a lower water level might help.
2) Pipe height, it is critical that the pipe is fully inserted, it is possible to barely slip it into the base and then it is already 1/2" or so taller, this has a similar effect as deeper submersion, their is a higher standing water level in the skimmer. I would suspect if someone had to cut it this and the booster ring being high were the culprits. The pipe should be 6.1" tall. I would give it a firm push into the housing, don't force it or you may break the base, but push firmly until it won't go in further.
3) Air adjustment, this will generally need to be closed about half way, the pump has power to spare, a bigger cup can be added and the air opened further on bigger tanks. It is important to keep in mind that as you restrict the air, you increase water flow, the pumping volume does not change only the ratio of air to water. I would start with it fully open and gradually close it after you have checked the two items listed above. Be sure the airline is not twisted or kinked, if it can flop over and kink, water volume will suddenly surge up and air volume will drop.
