I was going to put this in the last post but thought you had read the way I tested mine years ago.
Put a pint size paint can in the hose off the air filter box, tighten the clamp, pull the small hose off the blow of valve, give it a short blast of air, put your thumb over the hose, listen for leaks.
That's how I found the oem tmic leaking.
A bottle or any size can that fit's in the hose would work as a plug. You must have something over there that will plug the hose.
175,000+ miles, 5/20/12 new ej257 short block, 8/20/11 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. Also CHECK YOUR OIL, these cars use it.