Playing with my turbo...

[Dave]

I found it made a hell of a difference to my t2, remember your backpressure is a total killer and this releives quite abit. I would imagine it would work quite well on a gt15 but as Dan says your still only overspinning a smaller turbine and compressor to an airflow its less efficient at flowing, but in reality I hardly noticed any difference in lag and it spread my torque out lots more and it didnt suffer the dreaded backpressure surge you get at about 4k with one of these stock turbos where you feel like your engines gonna die.