I have a Syncro Doka with 1.9Tdi AAZ... there's more torque than the 2.1
WBX but not much difference in regard to top speed or or climbing a modest
hill on freeway/highway. The 1.9Tdi is heavier than the 2.1 WBX and
additional power is 110 compared to 90/95. I'd think a well tuned 2.2 or
2.3 WBX will beat it easily. If you still want a Tdi, maybe a 2.0 CR Tdi
from a Jetta or 2.5 Tdi from an Audi will make a noticeable difference.
I don't have the 1.9Tdi in my Doka anymore.