car is an 1.8t 150hp engine, stock internals, fitted into a VW Lupo, k04 turbo, 1.3bar boost at 27deg timing.. airflow ~215g/sec atm..theres more flow to extract from this k04..
Unless you're running one of the billet compressors from the FSI-TFSI K04's, there isn't much more airflow to be had from a K04 as 215 g/sec is about 270 CHP.
The largest of the cast compressors (2288 IIRC from the Mazdaspeed 3 and 6) is rated to 32 lb/min, but in the stock longitudinal turbine housing, you'll top out at about 28 lb/min or so of airflow.
Even with the largest of the billet K04 compressors, I don't know how much more airflow over 28 lb/min it will sustain. I know I've seen European dynos using calculated CHP that have reported 310-320 CHP on some of the FSI compressor K04 hybrids , I don't know how they arrived at that number. I would suspect that the WHP numbers would tell a different story....
Trust me, I've had the stock K03 / K04-15 / 2288 compressor Mazdaspeed K04 hybrid / GT2860 / 60-1 T3/T4 and a Comp 5566 setps all on my 1.8T. So I'm very very familiar with virtually all turbo combinations on those engines.
You say you're running 27 deg advance on this setup by the way, I'm taking it you are running water/meth injection? If not, I would strongly advise using it. Especially if you are trying to tune the stock ECU directly.
Water/meth is like a get out of jail free card when it comes to tuning mistakes. Trust me on that one lol. Lord knows I've made enough of them hahahaha.