Any of the shops in the workshop section in this forum should be ok -
some do new chips, some do reflashes, some do both.
note - I do not own a B4.
For my ride, I use West Racing in Osborne Park, well that's me.
A new chip or reflash would need to be done together with a tune -there is a tricky deadspot with that motor to overcome.
Be prepared for the advice to take out the 2 turbos and replace with a single.