I think that copper pimple is really just a noise suppressor. I looked at it tonight when I installed a new valve cover gasket as I had it sitting on a bench.
yea, that thing serves 2 purposes
1) noise suppression ... it acts a bit as a resonator chamber to mellow the sound of the intake under hard throttle
2) air reserve ... it increases the volume of air that is *freely* available under hard acceleration.
If you don't mind a bit of noise and have a free enough flowing filter, it is unnecessary ... then again, it really dowen't hurt to have it (other than possibly being in the way of something else you may wanna mount in there ...