Power and in some cases better spool. This little single starts to make boost where my twins did, but make MUCH more power up top with no taper in power. It actually makes peak boost about 200 RPM sooner than the twins did. In addition, when you go single, you have the advantage of large diameter tubular header/manifold which breathes better. The stock twins have a cast manifold that sacrifices efficiency for packaging. The single turbo can handle more boost too. My stockers were limited to 18 psi or so (400+RWHP), whereas this one can do 30 psi (650+RWHP). The newest Borg Warner turbos with their extended tip technology are even better...quicker spool and about 10-15% more power compared to conventional turbos. IIRC...your VW runs BW turbos..