Phil, don't you have different cam(s) in there too?
And you're right, the Suby even at it's 10.3:1(I think) compression ratio runs great on 87 octane. If the CR is raised then premium is necessary. I think compression is 11.5:1 using the SOHC head gasket. The DOHC gasket is thicker which gives the 10.3:1 ratio.
With 11.5:1 on 93 octane with 2.5 liters of free-breathing massaged heads? Sounds like 200hp to me!
EDIT: I believe the numbers I quoted were hot-rodded numbers from the NASIOC website. I think the stock EJ25 is somewhere from 9.7:1 to 10:1.