I've seen tests on this crap and well honestly that is exactly what it is, CRAP and BS. It also doesn't do your plugs any good, as double plat plugs don't seem to respond especially well to it.
I hope running that boost level you are not still running your factory turbos, or factory bottom end, intercooler, etc. If you are you are playing russain rulet` with your motor, and turbos. It will be only a matter of time before it goes bang in a major way. If that happens I hope you have extremely deep pockets for a rebuild. I've seen an R32, R33, and R34 spit its guts all over the place running high boost like that on a bog standard engine and fuel system. Not a pretty sight.
Back to the question. If you can't get the higher octane gas you require, don't drive the car. I've tried all sorts of octane boost and have found no viable increase in anything, and only provided a way to empty more money out of my account for no good reason. The other option is run the car at a low boost setting of .9 bar or less. Remember once you put shit gas into your tank, you have to put 5x the amount the good stuff to bring the octane back up in the tank as it is deluted with the watery stuff.