Major boost leak need help.

I had my car tuned a month ago, and it was hitting 14psi in the 80deg weather, then when it was about 50 outside i hit 18psi. But now that its only 80 again, im only hitting 9,10 psi. I tightened down all the couplers but it didnt help. I bought an air compressor but im not sure how to make a boost leak tester. I made a piece that plugs the inlet of the supercharger and it has a plug connected to it. I threw compressed air through the inlet of the supercharger and it wouldn't compress and make any psi. I think that one of the cylinder valves will always stay open is this correct? Is there anyway around this, how can i test it?

Has anyone make a boost leak tester, if so please explain how you did it.

Thanks!