If you just wanna increase the octane, you can add some Torco Accelerator octane booster.
https://www.summitracing.com/parts/t...010t?rrec=true
https://www.amazon.com/Torco-F500010...FC5EDEX25S6KVV
If you wanna add some real lead, you can add some Octane Supreme.
http://www.wildbillscorvette.com/OctaneSupreme01.htm
Both are probably illegal In CA. They may not even be able to ship to CA. Don't know. Users may have to smuggle it in.
Some mix in a little racing gas.