I built a device to pressure tester and hoses by using a piece of 4 inch ID rubber hose used for joining sewer pipe PN PCX 60-33. (Not very elegant but it works) A cap for 3 inch ABS pipe is 4 inches OD so it fits into the hose and can be attached with hose clamps. Drill and tap two holes in the top of the ABS cap for 1/4 inch pipe thread. Screw a pressure gauge (0 to 30 psi) into one and a short length of air hose with a valve and connector to your air source into the other. A nut on the inside of each for extra strength is a good idea.
The turbo inlet is 4 inches OD so you can attach the rubber hose directly to it. I highly recommend a short length of light chain around the turbo and ABS cap-- (you will have 125 pounds of force for each 10 psi)
The engine must be rotated so no piston is at TDC so you will not have any valve overlap. You can do this by trial and error.
Set the air compressor regulator to 60 psi and turn the valve on till the pressure reads where you want to test then turn the valve off and listen. Some leaks will not be noticeable at low pressures but will really squeal at 20 to 30 psi.
