Hello all,

I have a 97 Honda Civic DX 5 speed manual transmission.
First thing this morning I took it to get smogged (Drove it 20 minutes freeway first) knowing I have a bad Catalytic converter, and knowing I would most likely fail, but no check engine light so I tried anyways, and failed by one metric the NOx at 15MPH (But passed at 25MPH, it had less than the 15MPH test).
I know I could pay 700$ for a new catalytic converter, but would prefferably save that 700$ if I could pass some other way, by any means neccessary (Money is super tight). Is there anything I can do? I did seafoam. Spark plugs, battery, and O2 sensors were replaced 2 years ago on my last smog (Passed to the exact allowable NOx measurement). Fuel injectors were replaced 4 years ago on the smog before that.

I read online that possibly using denatured alcohol could help by raising the octane and messing with the timing of compression which would raise my HC levels and my CO (Which measured fine) but lower my NOx. I also read that the alcohol can damage rubber components in my car so it scared me a bit, but I also read about high octane racing fuel getting the same result, so I was wondering if it is possible to use racing fuel in my little Honda? If so how much should I use? Should I mix it with regular gasoline? what ratio?

Any help is greatly appreciated

TLDR: Car failed smog with High NOx readings, and I'm wondering if I can reduce that with racing fuel for the smog test.