You can't run a testpipe on OEM software or you WILL get errors.
You can buy a new turbo at
CTS Turbo for $659.00, which IMO is super cheap. If not get a used K03 from Audizine for $100.00
I would recommend buying the K04-015. It will run fine on the factory software then when you have time and extra money get TT225 injectors used form Audizine forums and a K04 software package.
The power isn't that much better than the K03, but they are identical size and for the price difference between the 2 its worth it if your stock turbo is gone.