By right side of engine, I'm assuming you mean the left side of engine behind dipstick? I'm pretty sure right and left are always from car's point of view, not yours...which is why in US, I always tell guys driver's or passenger side...just to be safe.
Anyway, rectangular black box maybe 1" thick, 3" high and about 5" long?
Isolate sound with a hose in ear or stethoscope. If it's hissing from there, pretty easy to get to and get it off. There is a gasket that can be replaced...and DISA's go bad pretty often from what I hear.
Many other places for air leaks, so before you go replacing a million parts, isolate well.
Upcoming comedy shows: May 20, Greenwich Village Comedy Club. 6 p.m. See Facebook for other shows and PM me if you can make one...love to see you there!
A recent set: https://youtu.be/995gLmVEVZk
Mangofy your E46!