Not what you asked for I know.........
Buy a T04Z *ball bearing* with 1.32 A/R and run 26psi boost, guarantee 500rwhp and 1 bar boost at 3600rpm minimum.
I used to run T04S with 0.96 rear A/R (P trim turbine) and they are similar to what you have now.
Forget "Hybrid's" I ran every type known to man, in both S4 and S5 frames with T04 front compressors (H trim) and Garret front compressor covers. These are total shit! they can spool early but suffer stupidly from the small turbine. A full T04 you have now will make 50bhp+ for the same boost levels all other parameters being held equal (yes its that big of a difference).
You can dick around with heaps of other "small turbo's" but nothing will ever beat the T04Z when fitted with the right turbine housing. its responsive and mega power at the turn of a knob
, you can make EASY 750bhp engine power with one on a 13B, or as little as 400bhp engine power (what ever this equals in your own local rwhp talk is up to you).
Trust me T04 anything less is a miss guided choice.