the SCC article was pretty informative. but definatly the most cost effective way would be to buy better gas. (they have 93 here, HAHA)
if you can get toulene cheap that will work too. the results from the SCC test suprized me though I thought it would provide more of an octane boost.
Just out curiosity why do you want to raise your octane that much? - EDIT Oops I didn't see your second post..
You should be able to run that compression with 90 octance and the NOS octane booster. I'm suprized that 90 is the best stuff you can get.
If you're careful with your tuning, you can run 11.8:1 on 90 octane gas. Just take extra care with your timing maps. Toyota sells the Celica GT-S with an 11.5:1 compression ratio, and that runs on 91 octane with a street tune conservative enough to survive if a retarded owner puts in 87. Tune yours well and you can get it run right on 90 and still make decent power. Of course, your power potential would be much higher with higher octane gas, but it will be difficult for you to make sure every tank of gas is consistent while mixing in octane booster.