The cheapest would be a 16v swap it is also very easy if you know what your doing or can be shown. They can be found all around in old B3 passats. After that all you need is a golf tranny with the bigger axels. I like to use the ones from the old 8v gli. Also easy to find around here for cheap. The 1.8T swap is way more expencive and not a novice job. Alot of wiring is involved and parts are pricey for the swap
Locate harry's U pull it in PA he has 3 locaions I have found all my parts for past rides in thesee bone yards
