Chaz try holding the peddle at 1800 to 2200 to build air without the fast ideal working. Try cleaning the contacts on the switch.Make sure your Governor is set between 112 and 118 cut out PSI
A budy of mine also suggested looking at the governor. Did it come with paperwork on how to set it?
You may have a problem with your discharge line. They are normally copper tubing or braided stainless hose. The heat from the compressor discharge will melt and harden the rubber inside the line creating a restriction. Remove your hose and see if it is still flexible, you can buy the correct style of hose at any truck dealer, they come in many different lengths.