Indeed the k04-001 is similar to the k03s, so in your case don't bother.
You could fit a k04-021, 022, 023. These are the variants fitted to the S3/TT/Leon Cupra R. There are lots of second hand parts available to fit them as upgrading to big Subaru or Garrett turbos are now fairly common place. If you go that route, then you might as well get a k04-02x hybrid which could give you 300bhp. You need to replace the exhaust manifold, downpipe, injectors, inlet etc for the S3/TT/Leon parts. A FMIC would be a good idea and then you have to have a remap on top.
Any of the 1.8T engines can take around 350bhp and similar torque figures if the map is good and isn't set to give too much low rev torque or too high rev power. Over that and you need to think about uprating the engine internals.
The bottom line is, you don't have to swap the whole engine to up your power.
Main thing is you choose your planned power level and then buy the right parts to get there. Do it once, do it right etc.
If your car is high milage, then tuners will tell you to renew piston rings and bearing, but to be honest lots of people run high mile engines and have no problems. I'm at 320bhp with 180000 miles. If it's not burning oil or making weird noises, then don't worry. The tuners like to cover their backs of course.
