It would be best to have the same size all the way through, 2" is usually
good enough for a 2.0, but I would use whatever size the factory used
for that engine, or a little larger.
I have always loved the power of the VW engines (water cooled) and
thought a 1.8 GTI 8v engine (101 hp) would be perfect, but that 2.0
I think is a 16V would be much better, and a turbo would make it perfect

Wild