Was the turbo built on the stock exhaust housing with stock exhaust turbine? Do you know, and/or is it a secret? Did you have an exhaust temperature or pressure gauge nad if so, what kind of readings?
I have pd130, which has custom software, cupra fmic and intake, and 2,5" cat back. Otherwise stock engine. It has been dynoed to 194hp/486nm(about 358lbs/ft, with stock sotfware about 155/380nm, weather 25C). Pressures peak around 1,7, but constant is 1,6. With the stock turbo the torque curve is not healthy, peak at 2000rpm, and goes down quickly. Next projects are on the way..
During the winter a bigger turbo will be made, using parts from GT20/vnt, MB 320cdi and BMW530d turbos (a specialist with 20 years experience and secrets on turbos..). Turbo is beeing made with few things in mind: spooling up around 2000 prm, good flow at high rpm -> which would also keep the high rpm exhaust temps and pressures low (hopefully pressure will stay same or maybe lower than manifold pressures). And plan to get a power range. We have in mind also that if I upgrade my injectors, the turbo should still 'get along' with more power.. Exhaust manifold will be separate, not the stock unit and nww donwpipe will also be made.
My software maker complimented the cupra fmic too. It is very efficient.