I NEED Boost... Opinions puh-lease

[eTiMaGo]

but, where's the fun in driving a turbo'ed car sensibly all the time?

You *could* use a variable potentiometer, or switches, to change the water temp tweaking on the fly, when needed.

As for what you need to tune in open loop, there are loads of options out there, personally I would want to get my hands on an inexpensive apexi S-AFC and a wideband O2 gauge to see just how effective this kind of tweaking can be, even without boost (the Yaris does seem to generally run quite rich in open loop mode, might be just mine, but there's certainly some power to be gained by leaning things out at high RPMs)