What you're saying is all true in theory, but the most comprehensive independent test carried out to date shows that the 7670 pegs right in between the gt30 and its derivatives and the gt35 and its derivatives in terms of power production and spool. i.e. it would slot in where a gt33 would have if there was such a thing, and far from the GT35 power/GT30 spool impression we were given (at least that's how I saw it)
Another thing I like about this test is that it was carried out at sane/reasonable boost levels, and not 35+ psi making them relevant to a wider audience..

http://forums.nasioc.com/forums/show...135597&page=31

As for the transient response datalog shown here: http://perrinperformance.com/shared/...frrepsonse.jpg

I'm sure this is a result of the GTX3076R's massive wheel mismatch compared to the EFR and not a matter of rotational inertia

I also found it interesting how the EFR dyno significantly outpowers the GT30 below ~2400rpm...