inlet and outlet. With the larger intercooler pipe, the flow is slower so less just shooting across. Some time put a shop vac to an intercooler. Years ago I calculated the engine flow and a shop vac flow that I had. Pretty similar.
You might fill part of the intercooler up with water when it is turned over. This will try to block the flow of air thru what is normally the top part of the intercooler. See what effect this has when you apply a shop vac.