But briefly, to gain power I enlarged the air tube ID and shimmed the plunger spring. Cost was $0.00, only rub is a drill bit is needed that will reach to the bottom of a 2-3/4" air tube. This is a little longer than some drill bit sets. The shim can be made from a piece of copper tubing, among other things. Lastly, a spring compressor is needed. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.