I went from a 2.0 to a 1.8t, though that was in a mk3

If you can buy it then buy it, its only worth doing a conversion imo with something that cant be bought (eg 1.8t mk3) cant see the point in dropping a 1.8t into a mk4 if you can just go out and buy one
as far as insurance goes, if you go with sky you will get a 20% discount and they also insure it as a 1.8 regardless of a conversion or not, my insurance actually went down after my conversion
