Here's a boost leak tester I made at my shop. 3" 3/8" wall aluminum tubing. 1/4" cap plate with a 1/4 Npt drilled and tapped hole. A couple of fittings from the hardware store. I have a 3" to 4 1/2" boot on it now that allows me to test from the intake horn. That will test for leaks at the compressor cover and hot side pipe connection at turbo. I run a constant 35 psi line to the top of my blow off valve to keep it close. Have tested up to 45 psi with no issues. I put a ring of weld around the open end of the pipe to act as a bead and have not had it blow off during testing. Let me know what y'all think.