I guess I'm confused.
You bought a turbo car, with the intention of tuning it for fuel that will make it have almost as much power as a naturally aspirated version of the same car? Seems like you bought the wrong car to me. If you wanted the economy and power of a 2.5i, then why didn't you just get a 2.5i?
No one is questioning your tuning abilities, or whatever your talking about with the Hyundai. But go ahead and tune your LGT to run 87 octane. Let us know how it works out.
Keep in mind, you bought a car that has "decent power" and all you want to do with it, is make less power and get worse fuel economy.