It was the one from the 210/225 TT/S3/Cupra R, i've never been in one but looking at the graphs they don't seem to do much at low revs.
This is what he said,
'the K04 is awesome. nothing like the VNT as it has lag, and with the small engine of the TDI it has a good amount of it. it takes getting used to as it does not produce full boost until 2500rpm. however, the boost is constant to redline and to top rpm as well....i was running 24 PSI which constant from 2500rpm to redline'
I don't know what injectors or pump he had