How do I retard timing with a sealed PCM?

[Pader]

I have an '03 Mondeo Ghia Auto and it is much more gas hungry than my former Zetec (manual trans). I am considering playing around with hydroxy as a main fuel. I am already building a circuit to fool the O2 sensors as I have installed rare earth magnets on the fuel line which must be doing something as my fuel consumption rocketed even further suggesting that the PCM tried to compensate for more efficiently burnt fuel.

Many people have had varying degrees of success with hydroxy generators including some that have reported running a car completely on the stuff. I would like to experiment with using high percentage use of hydroxy but the trouble is that my car has fixed timing (you cannot even test it) and because of the far greater efficiency of hydroxy as an exclusive fuel it is likely to cause explosive detonation if the spark is generated before TDC. I am looking for a way (preferably electronic) that I can delay the spark until 10 or 12 degrees ATDC. Has anybody any experience of this?