5w-30 weight oil warmed up to about 80C will dump at about 43psi on the Sti's. The Eg33 and EJ series motors use the same springs, OPRV, and shims. Verified this first hand just weeks ago.
There are more benefits to a dry sump system than just as a preventative measure for sucking off a, pardon the pun, a "dry sump". Zero oil aeration, case vacuum, etc, etc.
I do agree that the EG needs a better pump as Tom said. We're using the 12mm rotor as an upgrade for the EG's, and for now it suffices for most setups on those up to about 9K rpm. EG uses a 12mm rotor stock.
One must also not that you do not necessary have to run a full dry sump system to use a different pump. There are externally mounted wet sump pumps that could be used(in conjunction with a modified/gutted OE pump housing) It's just typical fashion for most going through with the trouble of running and external pump, to go the extra steps towards a DS system
