To the original question GTSBoy hit the nail perfectly.
The other problem the 7-blade wheel had, was compressor surge in the lower RPM on at least a RB25. I had one of these 7-blade devils back 8 years ago, they were called a GT3040 then, on a RB25 (tidied up head/ slight cc increase and that's about it)... And low RPM surge was a particularly annoying problem around 1900rpm. Tried to alter the tune a few times and just couldn't get it right and ended up going RB26 due to a few factors.
Still made good power, 270/280rwkw on around 17psi so similar to you, much more boost didn't net a whole lot of gain on PULP however. We did crank it up to 24psi and put 104 Sunoco through it for an Autosalon haha, walked away with 369rwkw so it still performed at higher boost levels but it required the fuel to do it.