I believe it's 3L or 3.25 with a filter change (which you should really do every time!)
I think your mate has just made you paranoid about your bike!
I don't know if those rubbers are there to stop engine heat getting back to you, or to keep the elements out of the engine, but they are best there if you've got them.
I was checking the fairing vents and stuff on my VFR750 a while back, and was interested to find that one of the main vents in the side fairing appears to be there solely to blow cool air onto my legs, rather than cooling the actual engine! Bit of a random fact there, but I don't think I ever thought too much about where the vents on my ZXR were actually trying to route the air...