yeah for sure, it might not be a bad idea to consider tuning for 91e10, i know when i had my subaru b4 rsk it ran heaps better on gas with 10%ethanol, as opposed to the chevron without any E, even though it was a lesser anti knock index rating 94 vs 91.
i would stick with the 14psi WG. "If the spring is too soft, even with no pressure signal to the actuator, the valve will open if there is enough exhaust back pressure, which will limit the amount of boost produced by the turbocharger" as your psi target will probably be around 25-27 psi. the diverter valve is how the stock boost venting system is operated on our cars, nothing really to do with power output. so when it needs to expel excess pressure from the turbo, it recirculates it back into the intake system IIRC. by sticking with the stock diverter valve system, you will not be getting any of the classic "psssshhhhhh noises when you let off throttle after making a pull. you may get some, but its very minimal in relation to a classic vent to atmosphere blow off valve like the TS dual port vr2 EM. the TS plumbback you mentioned will be a better way of managing those excess pressure changes, but again its a plumbback so it will not be venting to atmosphere. turbosmart sells a dual port which will give you the classic "psshhhh" noises that so many are accustomed to with turbo sounds. the new TS em VR2 bov's are the top of the line from TS as they bolt up directly to the stock/whoosh/s280 turbos like the stock DV does. there are also other options as well for vent to atmosphere blow off valves, which are usually chosen for a sound-preference like the HKS bov.
