lol pvc

pcv = positive crackcase ventilation, you cant really delete it but it can be simplified and a common mod is putting a catch can in the system to catch all the oily crap
you may mean the evap system? that can be deleted and is mainly junk especially on a mk3, same as the sai (secondary air injection) its just to heat the cat up faster from cold starts
things that can be deleted with no consequences (other than some codes) are n249 n112 and evap
check this thread on vwvortex
clickyand these
howto vids made by the same guy, just the first 2 are for the 1.8t. theres no catch can install vid yet but the first 2 vids are awesome info. I know the first one is an hour long, trust me watch it all it will guide you though the whole process of removing n249 n112 and the evap, and the 2nd vid guides you through simplifying the brake booster pipework and making the engine bay look tidier