egr: exhaust gas recirculation... basically feeds your engine its own poo instead of air and fuel. also its hot, and can give you premature detonation. though, it also adds dead space to cool the mixture... i hate it anyway, plus itll make the rear cyl hot from blowby.
pvc: positive crankcase ventilation. makes sure the block doesnt get pressurised, and pushes oil into the cyls. also happens to suck oil into the intake manifold...lovely. a ctachcan just catches the oil.
grab a manual, and have a look at what i mean, and how it works. basically involves blocking some vaccuum lines.